How can I last longer in bed without cumming

You can get special condoms which have a numbing agent in them which will help you to last longer.

Well, it all depends on what your doing. If you're having sex, then when your coming close to cumming, then slow down, and wait till the feeling goes away but stay hard. It can go on and on for as long as you like, but I do believe that if you keep doing that, you might just end up not cumming at all. If you are masturbating then do the same, stop when you're about to cum and try to hold it in. Good luck and if its sex, remember to use a condom.