Can you see any problem when taking these sleep meds?

That is a lot of various drugs that may interact with each other to increase potential side effects and interfere with their effectiveness or metabolism.
Take your list in to your pharmacy and have the pharmacist review the list.
They could enter them into their drug interaction program for
you. Make sure your doctor or team of practitioners know what you are
takin. You could do it online in Drugs.com site. You should be able to delete some of them to avoid falls or oversedation. Some of the antihistamines are
related to cognitive effects long term.

I think you're playing with fire. Clonazepam, all by itself, is a powerful brain-altering drug with considerable risk of dependency over time. Gabapentin is not listed in any sites I can find as something that shouldn't be taken with clonazepam, but it does warn of somnolence, dizziness, nystagmus....all signs of not being able to remain upright safely in the 'wrong' circumstances. Falling at night, half asleep, when needing to void, is a common danger to people on multiple medications.
I think the advice of seniormed is spot on....get a pharmacist to look at everything you take, everything, including any supplements, and your typical daily dosages of each.

Potential for problem(s), yes.

Agree with some of the comments previously made, and suggest -

1. Regarding potential pharmacist review, if your healthsystem or clinic has a pharmacist specified for reviews you might pursue that. For example, some systems have a team approach and a clinical pharmacist assigned to the team. They may call the team a patient centered medical home.
2. Regarding clonazepam, gabapentin, plus pregabalin, I am hoping part of your team have training in psychopharmacy (Psychiatry, NP, PharmD, other).
I don't believe the team would combine clonazepam, gabapentin, and pregabalin.
3. Caution on the doxylamine for sleep. Similar to diphenhydramine, although available over the counter for short term use in sleep, they aren't recommended by sleep experts.
4. The pharmacist and your team will benefit from a careful and complete review of OTC and prescribed meds. It may be eye opening for you. Please note the American Geriatric Society ""Beers" guidelines would recommend caution on many of the medications you may be using long term daily, including doxylamine, melatonin, meloxicam, and clonazepam.
5. Last thought, hoping the pharmacist and your team are monitoring the levothyroxine thru laboratory tests such as TSH, and your symptomatic response. In older individuals levothyroxine is reported to be overprescribed - patients with slightly high TSH but normal for age may be given levothyroxine without clinical benefit. For more information search on NEJM and Mayo Clinic and elderly and levothyroxine. Too much levothyroxine can contribute to insomnia, and other adverse outcomes. If I were in your place I would not use levothyroxine if my TSH was normal or just slightly high, particularly without symptoms. Of course, you might have been symptomatic and had a very high TSH, just something to be aware of.

Best wishes

It took me two years to taper off of 2 mg clonazepam. Terribly addictive drug but WOW does it work well! It has been associated with dementia with long term use. Now I only use .25 alprazolam if needed if I wake up in the middle of the night. I even worry about that! I use 10 mg THC along with 300 gaba and a low dose naltrexone at bedtime. Check out the benefits of LDN. It's amazing. The THC is medical. It works well. It does not have long term detrimental effects that have been noted. I use a tincture and do not inhale it. The antihistamine usage for sleep is also associated with developing dementia.

Thanks for your comments and leading ideas on what to work on. I've been on levothyroxine for many years but had no symptoms when the doctor had me start taking it, which was just due to my TSH number being out of range. I asked him at the time why I felt no symptoms with a TSH number being out of normal, and he just replied but that I'd eventually experience symptoms (unspecified) if I didn't start it then.
At any rate, I shall try cutting back on the antihistamine and clonazepam and maybe get to a safer level with those.

Thanks for the tip. I would never have thought of it.

Polypharmacy is dangerous.

I would agree with that. However, some meds I take I've have taken for many years. So, the "baseline" for my multi-year consumption of levothyroxine and clonazepam, doxylamine succinate, and melatonin, when compared to adding relatively new dosages of losartan, rosuvastatin, meloxicam. and pregabalin (Lyrica), well they seem less "dangerous" to me since I added one at a time far apart by several months. If I were to get a side reaction from one or the other, I'd know it shortly after taking it. Plus I get a number of regular blood tests that would raise red flags if there were any problem.

Is there a federal agency that has given its blessing to adults taking LDN (DOH, FDA?) as a sleep aid? Without that, I'm sure my doctor would not prescribe it for me. She's too conservative for that, she needs to go by the book officially.

To clarify the comment about levothyroxine, I will add the following story.
Let's say you are 70 years old, your TSH comes back slightly high at 4.8, with a normal range of 0.4 to 4.6. T4 is OK, and you don't have any symptoms of hypothyroidism. This scenario is common as we age, and unfortunately levothyroxine may be prescribed when the slightly high TSH could just be monitored. A second opinion from endocrinology might have advised not to start levothyroxine, or to lower the dose at this time. Insomnia may occur with levothyroxine, as well as associations with other problems such as osteoporosis and cardiovascular issues (atrial fibrillation). Levothyroxine is one of the top commonly recognized overprescribed medications, you search on terms such as overprescribed medications, Mayo,and elderly, and get more information if you wish.
Best wishes sorting out the medications, benefits, side effects, and if/when a given prescription is still indicated or should be considered for dose reduction and possibly discontinuing.