The circular rash on "various parts of your body" and the dime-size "dry patch" of your penis almost certainly are not due to an STD and probably is unrelated to the oral sex episode. Syphilis can cause a rash like that, but only in the "secondary" stage--which cannot come on only 30 days after exposure. If you had acquired syphilis from the oral sex event, probably you would have noticed an open sore of the penis. So syphilis might be theoretically possible, but unlikely. However, if you have had other possible exposures, going back several months to a year, syphilis might be possible. On the other hand, psoriasis is another good bet; ringworm; or any number of other skin conditions.
Penile bumps turning "almost pimple like" suggests a possibility of genital herpes. But if you have herpes, you probably didn't catch it during the oral sex episode you describe. The first outbreak of herpes usually occurs within a few days of catching it.
Bottom line: I'm not certain whether you have one skin rash problem or two different ones. Most likely neither one is due to the sexual exposure you describe. But the only way to know is to see a health care provider. Do it immediately; the penile lesions in particular will be easier to diagnose accurately before they get any older than 3 days. In the meantime, don't put any creams or ointments on any of the skin spots.
If you don't have a regular health care provider or dermatologist, visit your local health department STD clinic for expert, confidential, and low cost (possibly free) care.
Good luck-- HHH, MD