I did my first methotrexate injection on Monday. I did it in my upper thigh as well. The nurse said to choose a place that has a bit of fat. I don't have much in the way of fat on my stomach, so I'll probably keep doing it in the fatty part of my thigh.
For me, the injection was pretty painless and it wasn't sore afterward. I used to use the Humira injection pen and I would have bruising and a swollen reds spot for nearly a week after my injection, but I think the syringe is a lot gentler than the pen.
I've read about hair loss as a side effect, I'm keeping my fingers crossed that it doesn't happen. A couple things I noticed for a few days after my injection. I was more fatigued than usual and I've also been more emotional than usual. The emotional thing could just be a coincidence, I'll see if it happens next week when I do the injection again.
I hope methotrexate works for both of us! Take care.