If you were negative in Jan, you're correct that if you were newly infected, you'd be likely to have a lot more than a small, painless spot.
It also takes a lot more than some brief genital rubbing to transmit (and you aren't really sure that happened). It takes some good friction, usually the kind from penetration, though in theory, prolonged vigorous grinding could do it.
You mentioned that you had really dry, even ashy skin. You can get seriously dry skin on your penis. You can get eczema, dermatitis, etc., on your penis. You mention new soap, too - that could absolutely do it. I don't know what kind of soap it is, but you really only need a gentle soap on your genital area. Use Ivory or Dove for Sensitive Skin.
If it doesn't improve, ask your urologist about it.
And you could have non-bacterial chronic prostatitis. What does your doc say? Also, make sure to drink plenty of water, and avoid caffeine. Men with chronic prostatitis say that caffeine is one of their biggest triggers.
You can do another IgG test at 4 weeks, but my guess is it would be negative.
Quick update. The red spot had basically gone away but was apparent again after sex. Still very concerned.