I had unprotected sex a lot in the month of May then had an unusual period in June it was light then got heavy with blood clots then light with brownish blood. Exactly 3 weeks later I got a very light 2 day period with light brownish blood the last day. Could I be pregnant?

It's possible. Sadly we can't diagnose pregnancy online. The only way to confirm pregnancy is with a urine test, a blood test, an ultrasound, or giving birth.

Since you've had off periods since you had sex in May, try taking a pregnancy test. Make sure to use first morning urine and follow the directions exactly.

If that test is negative, wait and see what happens with your next period. It could be that you're having a few off periods. It does happen. But if the next one is off, and you're still testing negative, it's time to see a doctor and find out what's going on.

Good luck. :)