Feel great for weeks and then boom, nausea? What I ate?

I kinda have the same thing so I understand what you are talking about. I have to be very careful for what I eat. Dairy is bad for me..
For starters, you need to do a daily diary of what you eat and drink. I don’t know if you drink coffee or tea that you add milk too or sugars, but that can also affect you.
After you do this for a few months, go back and check to see if there’s anything that sticks out to you.
Also add good day bad day for yourself, That way, you will have a better feel of what is going on
I hope this could help you to start your investigation of what is going on
Good luck

Thanks. I drink coffee and eat cereal. Think it's the milk or
caffeine.

By tracking your meal or the foods you eat, it could help you figure out what the problem might be. And I hate to say it sometimes it’s just our bodies
For me if I have milk with lotta dairy protein, I don’t go far from the bathroom for 6 to 8 hours My body just cannot handle it
For you, it might be something else. I met a lady a few years ago, and she asked if we had mushrooms in any of the products we sold at the bakery. I told her I’m pretty sure it’s no and one of the manager says no there is no mushrooms. So it could be a lot of things your body is not liking
Do you check your weight regularly? Just to see if you put on a pound or two before you have these spells. Could be constipation, which is no fun
I wish you the best Figuring this out and sometimes it’s hard to do. Good luck

@mikejjb123 I’m also struggling with this problem, had a colonoscopy/endoscopy recently and I have a inflammation in my stomach. Another option is eliminating certain regular foods that you eat for a while and see if the symptoms return, there’s just so many possible reasons why you have this issue, truly the hardest part is taking the first step to find out what is causing it otherwise you just keep suffering!

Thank you so much for the insight Yes, more questions than answers for sure. Wishing you the best
.

@minnesota10 Thanks for the insight. Funny you ask. I pretty much eat the same each week on a daily basis. When I feeling good my weight goes up a couple pounds and then boom. Sweats and nausea. Cant say constipated. It's like a wave. I go 3 or 4 weeks feeling great and then boom! Then the cycle starts over again.

@mikejjb123 lactose. Maybe even the casein in cows milk. It happened to me slowly and when I was 62 whammo! Turned out I had ruined my intestines and my gums from continuing to eat lactose. I was lactose intolerant evidently since I was a kid and had occasional stomach ache. Coincidentally, I took a genealogy test with one of the companies that assess genetic issues related to things that are studied. Lactose intolerance is one of them and there’s only one Jean and I inherited it from both parents. Of course my brother had the same and knew he was lactose intolerant from the time he was 18. I’ve never had another cavity since I adjusted my diet. My gums were ruined. My that was bad and I could get very fatigued. Then I bought some lactose free feta cheese at the grocery store and I got a stomach ache still! Turns out I’m also casing intolerant so I can’t comfortably eat cow products. If you happen to be of Japanese, Middle Eastern or Jewish descent, you can count on that being your problem. I looked to my ancestors, eating habits, and I realized, even though they didn’t talk about it or have the science, they knew what to eat. So that’s how I eat. PS you mentioned the cereal change cereals so that you are eating a cereal without gluten you could be gluten intolerant as well. Do one at a time, though to see if you are one or both.

@mikejjb123 I understand what you just wrote. Hopefully, you could figure out what is causing the issue. Constipation hurts and you gain weight. Talk to your doctor maybe you need to add more fruit. For me, it’s grapes or raisins that help.
Good luck in your investigation of your life and body