painful lump under skin on penis

I'm an 18 year old male and have had 2 sexual partners (female), both of which have had sex only ONCE before me (protected).  After about 7 or so months of being very active, I noticed a hard lump (circular, 1-1.5mm wide) under the skin of my shaft.  There is only one lump.  Coloring was white, but not so off from my normal skin tone.  Now after 2 days of particularly intensive sex, the once before painless hard bump has become painful to the touch (just like a pimple), has turned pinker/redder, and has a little bit of swelling around it.  It is under my skin but attached to it, because I can isolate the bump as i pinch and pull my skin away from the penis.  I've had unprotected sex with both partners.  Only one (the most recent of the passed 5+ months) was tested for STD's.  The other I know for certain has only had sex once with a condom, other than with me.

Is it a pimple?  I looked up molluscum but that usually comes in clusters and there seems to be no dot or anything representing a "core".  I'm really freaking out, and I don't know where to find a doctor.  If possible I'd like to have a doctor check it out, but what kind of doctor do I look for?  How can I do it without health insurance and have total confidentiallity (from parents)?