What Causes Swelling In The Labia Minora?

About a week ago I started noticing a strange feeling in my vagina as if my underwear were rubbing me (kind of like when you wear tight jeans with a hard seam goin up the middle). The other day I started examining myself and noticed that one side of my labia minor is completely stretched out. I can even see it hanging out of the labia major. It's becoming very uncomfortable and I literally have to try to tuck it in so that it's not rubbing against my underwear. How could this have happened and what can I do? I have not been sexually active in a couple of months and I don't use any type of sexual "toys". I have been off work for a while and I just recently started back about a week ago. When I started, I was on my cycle and I was sitting all day with dress pants on and sanitary napkins. Could this have been the cause? Also, the first day that I started my period I was not home and I had to use a tampon (which I haven't used in probably 20 years). Could I have somehow pulled the skin when inserting the tampon? Any info on this subject would really help. It definitely feels very irritated down there and I do not have med insurance at this time. Should I be extremely concerned and get to the Dr. no matter what the cost or is there something I can use over the counter until my insurance kicks in in a couple of months?