Hi Aimee and welcome to Healingwell. I like you was diagnosed at 18 yrs old and I am now 54, so its been 36 years for me. When first diagnosed I was at my sickest. At that time I am sure they considered me severe, but since then I would say I am considered mild to moderate.
I think once you find the right treatment for you, you will start feeling much better. It might be hit and miss for a bit, but keep working with your docs till you are back on to the road to remission.
Since diagnosis I have had 3 daughters all adults now, been at the same job for almost 23 years, and married to the best guy in the world. I tell you this so you can see that there is life with Crohns.
Its not been all easy peasy, and there have been bumps in the road from time to time, but I have been able to enjoy life and so will you once you find the right treatment for "you". For diet you will need to find what works best for you. I personally follow a low residue diet all the time as this works best for me. You can google the diet and get ideas to help you.
I hope the meds work well for you and you start feeling better soon. Also, this is a chronic and incurable disease that must be treated at all times, so don't stop your meds cuz you are feeling better, or else you could wind up back where you are or worse. Good luck and big hugs!