Premature ejaculation

My partner and I have been together for seven years. For the first few years our sex life was great, not an issue. However over the past couple of years he has started to orgasm too quickly. He is 33 (I'm 30) and now when we have sex he will only last about five minutes, it never used to be this way. What's going?

I have spoken with him about it and he says he doesn't know why it happens and is getting a bit down about it as well. Does anybody know why it is happening or have recommendations for fixing it?

We have tried different positions and using sex toys on me so I can get a bit more enjoyment but as soon as we start having sex he orgasms.