I caught my boyfriend stealing and wearing my panties what should I do does it mean he is gay?

A preference in ladies' undergarments is no indication of his orientation and you should react in whatever way feels right to you. If this behavior is too strange for you to accept, you are wasting the time of both parties by continuing the relationship. If this behavior is fine, you might try getting him a few pairs of his own when his birthday rolls around. Give them to him privately, of course.

Before you react, however, you should take a few days away from him to decide how you feel about it. Does it truly bother you? Is it something you could get past? Reflect before jumping to action. You may find this seems an insurmountable problem at first and after a few days you may accept it and decide it doesn't matter. On the contrary, you may decide at first that it is not a big deal, but upon further consideration, you don't see him the same way.

Give it time and react based upon your personal preference.

Understand that this may be a fact he has not shared with others yet and don't use this against him whether you choose to end the relationship or not.