What can cause unintentional weight loss?

Recently I’ve noticed I’ve been losing weight without trying to, and I’m concerned. I’ve lost at least 10 pounds during the past maybe month or two months. I thought before I could lose weight and might feel better physically if I did, but I’m concerned if something more is going on. In fall 2024, I started eating differently, like having meat, fruit, and vegetables more, but I was still eating those things before just not all the time. I’ve concerned too because I’ve been having other symptoms, like have been constipated for several years and almost always feel there’s more I’m not getting out and like something is stuck. In summer last year, I started having a feeling of fullness right under my chest, and like there was pressure in it. In October there were several days or more when I had a streak of blood on my stool, but it wasn’t on the toilet paper when I wiped. There’s a chance I might’ve strained too hard, and like it kind of hurt coming out, but it could’ve been normal. This might’ve happened in summer too, but I don’t remember. Also in October, I felt like I started having chest pain or a pain right below my chest that I would feel in my back too. Sometimes it’s felt like it’s in the same spot on my front side and back side. The chest pain comes and goes, and sometimes it seems worse when I’m stressed or worried. A couple months or more ago, I felt like I was eating a lot but I was still hungry, like maybe I wasn’t getting nutrients from it.
Yesterday I had several bowel moments and went a lot, but after going my stomach and body just felt kind of tired. I also have felt like there was pressure maybe around my upper stomach, and almost like it felt like it could burst. In the past there’s been times when I felt like going to the bathroom or trying to go, put pressure around my stomach or right below my chest, and like there was a feeling of fullness. Since September last year, I’ve been having a feeling of impending doom and had a gut feeling at times like something is wrong. The impending doom feeling scares me and worries me, and it seems like it comes and goes but I can’t shake it. I have a doctors appointment in about a week