Ive been dating my long distance bf for a month were starting to have problems what should i do?

Okay when i text him or call him sometimes he doesn't answer or when he does answer my calls its always a really short conversation.and about something sexual.He tells me he loves me all the time but i am starting to wonder is it really true.His behavior is starting 2 make me question is he truly in love or is he just saying it to say it.I am also scared he might be cheating on me with some other chic.But he tells me there's nothing to worry about and i am the only girl for him.Idk what else to do anymore i am just so worried.