My mood

So basically, me and my boyfriend argue a fair bit. And a lot of the time it's over pointless stuff. But when we really argue I get so upset. I've always felt quite low, for a good 9/10 months. And for the past month or 2 I've been at my worst. I've self-harmed once and this was the only time, it happened after we had an argument and I was so angry and upset and felt so down about myself I just did it in the spur of the moment. Sometimes I feel so alone, I don't feel happy in myself, and with all the stress and arguments in my relationship it makes me so much worse. I often lie I bed at night crying, needing something to take the pain away. I am just so stuck with what to do right now, I don't want to speak to anyone about it because everytime I try I just break down crying. Has anyone got any advice?