Abstinence. 
I can't use hormonal contraception of any kind (the combined pill caused a particularly nasty, but rare reaction, which has left me disabled due to chronic, severe & very frequent hemiplegic migraines). Tried all types of progesterone only, nothing suits me. The copper coil caused joint pain (unpleasant but was just about coping), heavier periods (ditto), but then I got pregnant on it anyway & MC'd in first trimester, lasting about a month. So I don't trust it!
I mustn't get pregnant. My medication causes birth defects so it would not be wise. We were lucky that DD was born healthy. I didn't realise this until I'd got pregnant; any future pregnancy would need to be carefully planned.
I've asked about the diaphragm but was told it's not easily available & not sufficiently effective in my circumstances.
DH is getting sterilised as soon as we're sure we don't want another child. In the meantime, it's fairly rubbish.