I am playing a game now and it ended saying my opponent won but there were several possible moves for me. Why

Question

No pieces were lost. I was placed in check and had several options to get out of it.

Answer 1

Because regardless of your moves it would have resulted in checkmate.

Answer 2

If, as you say, you had several possible moves you probably lost on time.

Answer 3

If you are in check then you have at least one option to get out of it at that moment, although you might not figure it out.

If it declared you won, but said you have several possible moves then either you're not playing chess, or it means "you had several chances to get out, and you didn't take advantage of them.