My older daughter is currently on MTX. She does not have hair loss as a side effect. She has mild nausea and fatigue the day after the MTX shot (she does it on Friday nights, so she can rest the next day), but no other side effects. She takes folic acid daily and that helps with side effects. She is also allowed to take Zofran for nausea if necessary.
MTX works well for the peripheral joints - such as the knees, hands, elbows, ankles etc. It is a good option if you have arthritis in those joints.
If the spine or SI joints are involved, a biologic is usually used. Since you're already on Humira, if those joints are involved, they may either up your dose or switch your biologic.
Are you seeing a rheumatologist? Spondyloarthritis is associated with Crohn's and needs to be treated by a rheumatologist.
Ron, just FYI, a chiropractor is not recommended if you have SpA - they can cause a lot of damage. You didn't say what type of arthritis you had - osteoarthritis is also very common in the lower back - but I figured I'd tell you.