alternative to mini pill

I went on the mini pill 3 weeks ago, and within days of taking it, I got a very heavy period, associated with period pain and back ache. I also felt very nauseas. I put it down to the pill, and stopped taking it, and everything cleared up within 48 hours. I didn't know if it was a coincidence or if it was the pill, so I went to the doctor and he gave me a prescription for another pill. I'm worried about taking it as the period pain was awful and the bleeding was very heavy. I've never experienced heavy periods or even period pain before.
Are there other alternatives to the mini pill? I'm not keen on getting pregnant any time soon, and looking for some protection for at least the next 18 months.

If you're b/f you can have implanon.
It is similar to the mini pill but is a much lower dose due to being directly relesed into the bloodstream. Unfortunately it didn't agree with me and I had it taken out after 1 year but I'm sure it's not the case with everyone.
There is also the IUD if you want to go there, though probably not if you're looking at TTC in 18 months.

Yes I am b/f. I've tried the implanon before and it didn't agree with me either.

I have the mirena IUD. It lasts for up to 5 years but you can get it removed any time and you can start TTC as soon as it's removed. There are a couple of threads about it on BB if you want to find out more or ask any questions.

I hade the same issues and ended up getting the depo injection. So far it suits me just fine and it only lasts 3 months.