Hi Amy, welcome to the club. Sorry you had to join us and I hope you don't have to stay in the club for too long! It's no fun being undiagnosed, but there's a lot of great people in this club so lots of support and information to be found here.
I think we've all heard from various docs that it's all in our heads, or it's IBS, or it's depression, or we're just crazy. You know your body, you know you're legitimately ill and it's not depression or "just IBS" (you may very well be depressed on top of all this, that's certainly not uncommon, but depression isn't causing your intestinal illness!). You just have to keep trying with different doctors until you find one who listens. Unfortunately, sometimes that takes a few tries. I once had a doctor tell me I "look depressed" (really, you can clinically diagnose someone based on how they look now??) and I also once saw an urgent care doc who told me it's IBS - when I explained to him all the reasons why it's not, he yelled that he's not a GI doc and then stormed out of the room! There are some really terrible doctors out there and it sounds like you've met some of them. The good news is, there are good doctors out there too! You just have to seek them out.
With regards to CRP, my doctor told me that anything over about 8 or 10 would be considered high. When I was having some mild symptoms, my CRP was at 17, and now that I'm doing pretty well my CRP was last tested at 10. Some people seem to stay in the 20s or 30s with miserable symptoms, and I've seen some on the forum say their CRP was in the hundreds - I believe most of those people were hospitalized at the time though! And from what I've read, about 10% of people with Crohn's or colitis will have a normal CRP even when they're in a terrible flare. So it's not a super reliable thing to go by, but it's okay. The other thing about CRP is, as my doctor told me, it is a general measurement of inflammation. When my CRP was at 17, I was having some trouble with my arthritis, and my doctor said that my raised CRP could have been due to inflammation from my arthritis, or inflammation in my guts, or neither or both! So it's not entirely something to go by, but it can indicate a general measurement of inflammation in most people.