I'm not a doc, but I have mild lymphedema in my left arm (from mastectomy sept '05). The pulling and tugging you feel is possibly (and I say possibly since I don't know you or the circumstances but I'm as active as you are) mild/moderate swelling that has accumulated above the sleeve OR (this is my general problem with the tightness) sometimes we don't use the arm like we used to when we were young and it just tightens up. I have to continually stretch my arm out with the exercises so that it doesn't return to a tight state. I use the gym nautilus machines for that when I'm there...works wonders.
My wing area, under the arm (not the armpit but to the left of the left breast) also gets a funky feeling every so often, usually from some mild swelling.
Do you know how to do manual lymph drainage and massage? That helps a LOT for me. You should try to keep the arm's range of motion exercised as much as it will allow. I do a few shoulder round ups and then outstretch my arm in as many directions for as far as I can ever day in the shower to warm it up. I still get pains every so often, but mostly it's ok.
Don't forget to wear your sleeve. If you are still concerned, you should ask your doc to have you re-evaluated. And don't forget to get new sleeves every so often. They come in colors now, FINALLY fashion comes to compression sleeves.
Dear nay24: Without evaluation, it is impossible to speculate on what might be causing your discomfort. You should contact your doctor for evaluation if you are concerned.