Can my boyfriend tell if I am a virgin?

No. Nobody can know for sure if you are a virgin unless you tell them.

If you have already had sex, the only thing that might have changed in your body is that your hymen (the thin layer of skin that partially closes the vaginal opening) is torn.

We say might because some women have a hymen that is so small or so elastic that it doesn’t tear even when they have sex several times. 

In addition, some women are born without a hymen, so they have nothing to tear.

But assuming that your hymen is like most women’s and that it did in fact tear the first time you had sex, this is the only thing your boyfriend might notice (assuming he is experienced enough to know what he’s looking at).

However, he still won’t be able to conclude that you have already had sex, given that several nonsexual activities, like bicycling and horseback riding, can cause the hymen to tear.