Hubby won't last

My husband and I have been trying to TTC for some time now. I am currently taking clomid, my doctor wants us to have sex every other day from cycle day 12-30 since my cycle days are longer than normal..... Well after about 4-5 months of having to do clomid my hubby just can't last any more. I know this is TMI, during intercorse my husband will be hard as a rock and then out of no where he will get soft. It's very frustrating and ruins the "mood". I start to think there is something wrong with me, or my husband just isn't in to me anymore. Is there something he can take OTC to make him last and finish? I don't want him to take something that can make his sperm count go down. Help!!!!