Are you sure that the pain during sex is due to the crohns? From what I read, I didn't really see a connection, but I'm not too educated in crohns.
I'm just thinking that if you recently started having sex, you might want to rule out other causes like lack of lubrication (use store-bought lube) or any gynocological issues. Are you having bleeding during or right after sex, and is it bleeding from your vagina or in your digestive tract?
I think you should definitely mention it to the doc who is treating you for crohns, and if you rule out other common causes of painful sex, (rough sex, lack of lubrication) then you might want to see a gyno as well.