I can't handle masturbation?

I got a g spit vibrator with a bunny for the clit. I'll attach a picture. My issue is that whenever I'm pleasuring myself or someone else is (my bf), it's too much and I can't handle it? I don't really know how to describe it. I was using the vibrator and I ended up stopping because the stimulation was so much. Any stimulation seems like it's too much if it happens for too long. Any tips?