Hello, welcome to the forum!
As cross-stitch says, I've been dealing with these issues since my teenage years, and while I'm no longer a teenager myself, I really can relate to the unique issues that come with having a chronic illness while contending with growing up.
I have had joint problems for at least 12 years, and was incorrectly diagnosed with Fibromyalgia for a while before having the diagnosis of inflammatory arthritis. In my case, my doctors think that I have seronegative RA, which means that I have a form of rheumatoid arthritis but it doesn't show in my blood work or on scans. We are currently still testing this theory and making steps to ensure that this is the correct diagnosis, as Maya says, SpA is a real possibility with Crohns, so I'm taking steps to make sure that nothing has been missed.
X rays are a good starting point when looking into joint issues, but they dont pick up everything. If you can request bloods, then it may be worth asking them to check your vitamin D and calcium levels, and also ask them to see how your iron and B12 levels are, as having lower than normal levels of these vitamins and minerals can contribute to joint pain. I don't know where you are so I'm not sure how easy it is for you/your parents to request imaging etc, but its worth thinking about if you can, especially if your other testing draws a blank.
In terms of pain, heat is great, I have an electric heating pad that I can lay on or place on aching joints, and it makes a really big difference, it's even safe to sleep on so I can use it at night. Hot baths are also good, soothing muscle rubs can sometimes help but personally I don't find them very useful.
I know its difficult when everyone around you has so much energy and wants you to get involved in things, but try to pace yourself if you can. I find it helpful to try and prioritise the things that really need to be done, and let smaller things slide if needed, its good to try and leave yourself a little energy to do something fun too. Remember to rest if you're feeling really tired and try to be kind to yourself. You didn't ask for all of this to happen, so it is in no way your fault and its OK to take a break.
At the moment I can't think of anyone specific to tag for you, but it could well be worth trying out the teenage section, its quite quiet on there but usually people will respond when they see a new post.
Please don't be afraid to ask us anything you like, or even just rant. Although many of us are older, we do understand the trials of having chronic illness and having to cope with the pressure of trying to keep up with regular life. You are not alone in this and we will all do our very best to support you.
You are also very welcome to message me if you feel you'd like a one on one chat, sometimes it's easier to chat to one person rather than post openly to a full forum.