Raspberry Leaf Tea increases the nutrients to your uterus. Evening Primrose Oil helps to promote contractions. Take the Evening Primrose Oil as it says on the bottle but also insert 2-4 caps high into your vagina at bedtime. Put a pad on as things can get a little messy in the morning.
I would recommend that you use them together. You can also add black Cohosh 40mg a day. It should be available at your chemist or health food shop.