It could also be drug-induced Lupus, given that you are having symptoms after Remicade infusions. My daughter got drug induced Lupus while on Entyvio. She had horrible, debilitating fatigue, bad joint pain and a butterfly rash on her face that came and went.
The blood work they did was ANA (which was positive) and anti-histone antibodies (also positive). She does have Ankylosing Spondylitis (has had it for years), which is a type of arthritis associated with Crohn's. So she was already seeing a rheumatologist.
Once the blood work came back positive and her GI and rheumatologist were fairly certain it was drug induced Lupus, they stopped the Entyvio. They said it would take 3-6 months for her to recover. She felt better in about 2-3 months.
The kind of arthritis associated with Crohn's - Spondyloarthritis or Ankylosing Spondylitis - is not usually associated with a positive ANA. It could happen, but your symptoms sound a lot more like drug-induced Lupus to me.