Communication Issues/Infidelity In 5 Yr Relationship

Hello, First time posting and looking to get a listening ear to try to help get into a better spot in my relationship with my partner of over 5 years. So to begin I guess I'll start at the beginning of our relationship. When we first started talking we both were pretty fresh out of a relationship mine of over 3 years and his of 8 months. We talked for about a month before meeting for the first time. During this first meeting I had a friend drive me to meet him and ended up stranded with him for a little over three weeks trying to find a way home so, needless to stay out relationship got pushed into over drive pretty quick and we started to really build a emotional connection. I left right around Thanksgiving and before I had even been gone a day we were both feeling that we'd like to continue into a full on relationship, I returned right before Christmas and never looked back. About 2ish months into the relationship my partner had befriended a guy who he worked with. He introduced me to said friend and we all began hanging out together on a relatively daily basis. The friendship had grown to a point where we all decided to try a threesome. It failed horribly, I realized that the friend was more interested in my partner than anything going on in the moment. So we decided to end anything sexual and stay strictly friends. About a month later (3ish months into relationship) my partner decided to reveal to me that him and said friend had been having a fling behind my back and that he was feeling so bad that he could not continue to hide it and had ended things with said friend. We decided to move forward and I decided that I would rather work on us than lose our relationship. About a year later I am working and my partner has been laid off from his job leaving me to provided for us both on my own. This is when stress really begins to take it's toll on the relationship. I start feeling that I am the only one trying in the relationship, but I love him and I'm willing to do whatever I need to keep things going. At this point I'm feeling overlooked and beging looking elsewhere for attention, trading pics, but never leading to any hookups. My partner finds out and it starts us back over at square one in our trust for each other. Year three we are in the process of moving and being homeless due to me being the only provider of income still. Partner has had jobs off and on but nothing lasting more than a couple months. At this point I feel absolutely hopeless with no help and feel like I am not being heard out when I say that I am needing help and that I am so stressed to the point that my depression is taking over and making me sick. But like always I love him and he loves me and we continue on. Year 4 this is when our relationship gets the biggest test yet I am diagnosed with Acute Myeloid Leukemia, at this point partner has been working for about 5 months at current job things are getting to be okay and then wham I'm stick deathly ill and no income. He loses his job due to me being sick and it leaves everything falling back on my shoulders again, we are now homeless, no income until short term disability kicks in and unsure what is going to happen to me. Partner has 3 jobs that last less than a week during year four. I am paying what I can in the moment and finally receive the best news I can I've received help to get us into an apartment to get us started once I am out of the hospital and in remission. Moved into new place and I am still currently the only income provider taking care of all bills while trying to recover from multiple rounds of chemo and working part-time. Year 5 where we're at now things have just been slowly feeling like they're desentigrating around me and I feel like I am alone, no help no emotions nothing. I begin reaching out again and this time it got to the point where I actually met up with someone to cheat but when the time came in just couldn't do it because I was doing it behind the person I loves back. He finds out and we split up. We go for a few days and decided we will both go to counseling and work on us and building our relationship from the rubble. TLDR: What are some tips for building better communication in a relationship so the other person doesn't feel attacked? What if anything can be done to come back from infidelity? When is love just not enough? How do you handle needing help and not getting it?