Are contracting multiple simultaneous STDs common?

STDs. If you are promiscuous and not using protection anything is possible.
Yes. Obviously, obtaining an std infection means one is engaging in risky sexual behavior with other at risk individuals. Therefore, there is a risk of acquiring other infections at the same time. For instance, when one gets chlamydia or gonnorhea, doctors with frequent just assume you have the other because they often go hand-in-hand.