Very scary sex scare. Stupid and had intercourse with stranger. Should I check for stis and hiv?

Absolutely. Many women now carry condoms so that if their potential partners do not have one they can provide protection and refuse to engage in sex if unprotected. And do not take anybody's word for whether they are HIV infected or have engaged in risky behavior. People lie, or simply may not be aware that they are infected. And you are correct in checking for multiple forms of std and not just hiv.
Yes. I very much agree with dr raff. When you become sexually involved with a stranger - you have no way of knowing what you were exposed to.