When you say white blisters how do they look?
Are the ones on the penis the same as the ones on the back?
If so it is likely it could be molluscum.
Molluscum can spread from dirty towels or even a hot tub.
Usually kids get it but am wondering if you used an infected towel on your back and genital area.
In any case go to your GP.
If it is molluscum they will use liquid nitrogen to burn it off.
Molluscum looks like this:
