Spotting and bleeding inbetween periods after unprotected sex. is this an std?

Unlikely, but possib: If one has an infection on the cervix, it's possible to have bleeding after sex, though very unlikely. More unlikely at 43 years is hormonal fluctuations. As we age, we tend to experience greater swings in our ovarian function, thus producing breakthrough bleeding. Another cause is a polyp or fibroid, for which you would need to see a doctor to diagnose. If continues, that would be a good idea!