Advice needed:/

So I have been TTC for 19months now and obviously that has deeply upset me for a long time that it doesn't seem to be happening, but lately it is taking a toll on my relationship as my boyfriend is getting really irritable and moody because it is not happening. He has just came out with "we may aswell not bother having sex as nothing's working". I can't help but feel he is blaming me for not being able to get pregnant as of yet and is really upsetting me. How can I try and lift his hopes and not give up?