My mom just found out that I was raped about 2 years ago and she was going to take me to the gynecologist to find out when I lost my virginity and to see if I am sexually active and my boyfriend and I recently had sex like a month ago so I want to know if there really is a way to find out if I'm sexually active and when the last time I had sex was... if so what can I do to make it look like I'm not

First depending on where you are a OB/Gyn may not be able to discuss your sex life with your mother without your permission.

Second, they can tell if sex was very recent like within the last few days. But a month ago they can't pinpoint.

Third, you should not be lying to your parents. If you can't tell them you are sexually active, then you shouldn't be.