Your best bet is to just go to the doctors, explain the situation and they'll do some accurate tests. And if u aren't pregnant they can give u some peace of mind about what's going on with your body.
Some women do not have periods due to being thin, or being extremely active. Before i was became pregnant my periods weren't much of periods. They were extremely light pink and lasted 1-2 days
Blood test? Or call your doctor sometimes having sex messes with em.