Bleeding after sex third trimester?

Husband and i decided to get down and dirty tonight and i have had some bright red spotting since (almost 2 hours later and there is still some blood when i wipe). Not in any pain or having any cramping. Am currently 30 weeks and debating on how much longer to wait before calling the midwife or going to L&D. How much is too much blood or how long is too long to have bleeding?