My husband cant do sex twice in a day during ovulation period?

we want baby and my husband's sperm count is very law. And our GP said to having sex twice or thrice during ovulation period. But my husband can not do sex each day twice during ovulation period. Lots of time i try to excite him he become excite but during intecours his sex orgen become loose and he stop doing it and some time he wants to do sex but his liquid dosent come out and he stope doing it. some time i feel that he has lake of liquid. he can do sex once in two or three day so how can my husband increse his sex twice and thrice each day during ovelution? please help me please give me some medicine or anything for that.