Panic attacks during sex??!

Every time my so and I have sex I'm fine but the minute he fingers me or I get close to orgasming I have a panic attack and have to stop. I don't know why this happens, but I don't like it. I love the guy with my whole heart and I don't like having to stop having sex because I start to panic. I've never done it before but they started once I got on the depo shot.