I’m struggling with my partner because there is no love between us. He is not affectionate enough for me and I have been asking for affection in multiple ways without anything changing. He knows I am in a bad place, but he keeps saying he is doing everything he can and can’t do more. If he isn’t giving me what I need, I will have no choice but to end this relationship. Is there anything I can do to convey how serious this is and how his behaviour is causing me real harm?
You don’t need to do anything if you have been specific about wanting affection. You have been direct, and he has conveyed his inability to do more, which gives you all the information you need to figure out your next move. A relationship should meet certain needs, without which it starts to wither and die. If you aren’t getting what you want out of this, and your partner is okay with the way things are, there is a mismatch of expectations that needs to be considered. This also raises questions about respect, because it sounds as if you aren’t being taken seriously enough. Think about that too and ask yourself if you feel heard. If you don’t, this won’t work for much longer.

How do I know when to make the first move if I have feelings for someone? I recently told a guy that I liked him, and he promptly started distancing himself from me. I am just afraid to say anything to anyone since that happened.
You don’t have to second-guess yourself based on how one person has reacted. If you want to say something to someone, you should be able to without fear because you aren’t responsible for their actions. An adult should be capable of articulating how they feel, irrespective of whether that is interest or disinterest. If someone isn’t mature enough to do that, it isn’t your fault and you shouldn’t have to change who you are to accommodate that.