Tips for lasting longer? Help me!

I've been with my boyfriend for 3 months now, he's absolutely head over heels for me and I adore him too. But the thing is... He's crap in bed. Really, really bad. To the point where we just don't bother trying, or it takes longer to get undressed beforehand! He honestly lasts about 3 minutes and it really embarrasses him, any tips for how to get him to last longer? It's starting to create a barrier between us 😞 (we're both 18 by the way and not each other's firsts)