Not Hitting the Spot

A couple days ago or so my boyfriend just started finding/fingering the right spot on my clit and it was so great and I orgasmed pretty quickly. After the past few times he hasn’t been able to get it and if I orgasm it takes upwards of 40 minutes and his hand gets too tired to make it that long. I’ve tried masturbating with just my hands to see what I like, but the only thing that gets me off masturbating is a vibrator, but I don’t want to use that with him. HELP!!!