Premature ejaculation. Lost ejaculation.

I am a married man and I noticed too many things while having sex with my partner.whenever i sex i noticed ejaculation very quickly ,while i have oral sex and whenever about to start intercourse i  sometimes seen that my penis lost ejaculation. But this is not the same in all the times when i have sex , sometimes it comes to an end without any problem but that last for 2 or 3 minutes.From a few days i am using oil on my penis just before intercourse to avoid the problem of ejaculation lost and this works well but it last for a few seconds in rapid motion.kindly give me the answer can i make my partner pregnant in this situation or it is necessary to have sex few times in a day to make her pregnant. And how can i make myself last longer in bed to satisfy her.