weird symptom, cause for concern?

[ohmygeisha.livejournal.com]

So, I started noticing last night that my vagina felt strange and a little painful. At further examination when I woke up, I noticed a change in the way my vagina felt with my fingers (particularly in the opening, but also there seems to be a pea sized lump directly above it). My first thought was that my cervix is shifting a bit, or sitting low, but I've never really noticed discomfort from it in the past. I was also peeing quite a bit last night. I'm a bit worried I may have an STD since I found out my ex was cheating on me throughout our relationship last night. Also, I have an IUD (Mirena). Any suggestions on what this could be? Do you think it's urgent, or should I get checked out at the hospital? (I'd rather wait until the week when I can see my own doctor).