Sex to soften cervix! Help!

I am 38 weeks and 2 days. My LO hasn't dropped yet and my cervix is closed and not soft at all. I am being induced in 5 days because of slight preeclampsia. I asked my doctor if there was anything I could do to move this along before being induced and he said sex is the only thing that has shown to possibly help. I didn't think to ask how often we should have sex for it to make a difference in my cervix.. I read on a forum 3 times a day... And that just makes me cringe thinking about it. So if anyone knows from personal experience, let me know! I need all the help I can get to be ready!!