Many women feel more vulnerable and emotional just before their period. That’s an absolutely normal response to the hormonal shifts going on in our bodies.
I think there is more to it than that, though. You are carrying a heavy load. At only 22, you are supporting three people. To your credit, you are doing it without complaining and you are making every effort to be positive. But it sounds to me like the stress is getting to you. Usually you can handle it. But when you are premenstrual, your defenses crumble a bit and you have more difficulty coping.
There are at least a couple of ways to deal with this. Internally, you can remind yourself that these episodes always pass. You can let yourself have a good cry and sleep it off. Externally, you can make more of an effort to reduce your load. You didn’t mention why you are the only one paying rent. Maybe it’s time for a family meeting to work on the financial problems together. If your mom is disabled, can she apply for disability benefits? Can she find some work? Is your brother old enough to be more helpful — if not with money, with more help around the house? I applaud your efforts to help your family in hard times. but it’s also important that everyone in the family does their part — both for your mental health and to keep the relationships in the family healthy.
I wish you well.