I'm not ED but sometimes when i engage in sexual activity and my partner skip foreplay, i cant get the erection to be hard enough. Other than that when we went through a nice foreplay, it became a stone
try OTC arginine supplements, or look into prescription drugs like Cialis.
otherwise just man up and straight put your dick in girls mouth for some easy foreplay, whatever turns you on, be shameless about it. Dont ask, girls dont like it. they are in your bedroom for a reason already. if they bitch and whine about it, simply stand your ground and continue. If they still act retarded just leave them and NEXT!
It's a question of arousal then, insist on some foreplay. Meds and arginine can help, but they don't do anything if you're not actually stimulated. Also exercise and PE exercises really do help with erection strength.
Citrulline Malate, better hydration, probably way more exercise, lose some weight, check your hormone levels, the list goes on. If it's a mental thing though, then you just have to figure out why you might be having performance anxiety.