HELP! HAVING 3 SOME TONIGHT!!

I CAN'T KEEP HARD IDK WHERE TO POST. MY MIND WANDERS AND GOES INTO DEPERSONALIZATION AND I LOSE MY BONER . my gf and i have had sex twice now and i could get hard with weed just couldnt cum. i'm not on any psychmeds. WHYH CANT I ######6 CUM ######6 FOR 4 STRAIGHT HOURS? AND THE 3 SOME THEY WILL BE DISSAPOINTED IF I DONT! i've been up for 3 days straight too n cant' sleep now to late
what do