Condoms. Just get a good one like Kimono or something. And use a really good lube like the ones offered by Pure Romance. I know that condoms have a bad rep, but they are the easiest, the cheapest and fairly reliable. They have no side effects, unless you are allergic to them. Many people don't like them, but let's be real, sex is great with or without a condom.
And start charting your cycles using Toni Weschler's method. (Welcome to Taking Charge of Your Fertility) You might find that living primally will even things out a little more for you, then you can only use the condoms when you are in fact ovulating.
That's my two cents.