Ovulation here & DH is "down" :(

Looks like ovulation is fast approaching - DH and I have BD'd the last 2 nights and I was planning for it at least the next 2 nights, too.  Last night for the first time ever DH had some trouble maintaining an erection.  He's got a lot going on at work and I'm not making matters better by hounding him for sex.  But I feel like it's pretty important tonight!!!  Any advice?