It's probably what's termed a 'wish fulfilment' dream. When you are not having sex in real life, your mind balances this out by giving you more sex dreams. This is to balance out your mental health and keep you sane.
In some cases it can be prophetic, but as you've just split up not long ago, I wouldn't concretely take it as prophetic. It's not impossible, though.
My 'ex' gets physical after I have dreamt it. But every person is different.
