Blisters on Inner left butt cheek

[Pregmom123]

OK, so I have what seems to be a small cluster of sores on the inner left butt cheek. On the LEFT SIDE ONLY of my butt cheek, there is irritation, and the skin has little bumps on it, indicating a rash of some kind. They look like little pimples, or you know when u get burned and the burn fills with that clear pus? Well like that but a small patch of small ones.  These symptoms only appeared today, although I was experiencing some discomfort yesterday, as well. I have irritation, and slight burning/soreness but not much itching.
I do not think its an std or anything of that sort because my vaginal area is completely clear and normal & my anal area is clear as well & Ive never had anal sex for them to appear on my buttcheek. Im also 23 weeks pregnant & was told alot of things can appear when pregnant. PLEASE HELP ?!