If my gf has been on birth control, regularly. and has been for over 4 months. and we know her menstral cycle. plus the next morning, take the morning after pill, is it at all safe to not use a condom and ejaculate inside of her?

Probably: I believe you indicated that your gf is using the bcp for 4 months and she takes the morning after pill after every sex. First, the bcp is very effective but not 100%. Second, she does not and probably should not take the morning after pill every time - too much hormone. Third, the condom is also protecting you from std. If you want safe sex and extra protection then use condom. Talk w/ your doc.