Hi maria0122!
Hi I am 19 and feel very similar to how you are feeling. I recently started birth control for the first time and feel very different on it. I do not know if it is strictly the birth control, natural hormones, or a combination. How long have you been off birth control? Because it could take some time for your body getting back to its usual self, however I am no expert about that so it’s just a suggestion if you want to explore more with your doctor or something 🙂
You said you have become more emotional, especially around your period. That should just be hormones/PMSing however if what you are saying is that your period mood symptoms got worse, is it perhaps you are a late bloomer? Because it could just be your hormones are kicking in more. I am a late bloomer and never understood why in middle/high school periods were so intense for some girls. Now I am starting to see at age 19 (more irritable, waterworks while watching TV, never got cramps but will get them once in awhile now)
You talk about how blessed your life is. That’s wonderful you recognize and feel that! 🙂 However, are there any small stressful unresolved feelings/situations you have in your life? I noticed for me it makes my PMSing sadness/madness worse if there is something worrying me. If there is nothing too bothersome then I suggest just watching a heartfelt movie/TV show. It just gets those feelings you have no idea why you are feeling out. My roommate and I used to have movie nights strictly to cry to when we were feeling stressed/emotional about silly stuff we couldn’t really control ya’know haha.
Oh, also you mentioned you get insecure and having your worst downs when you are in some sort of relationship with a guy. Getting close with anyone, especially with someone you are romantically interested in, takes a lot of trust since you begin to allow yourself to be vulnerable. I do not know about the guy(s) you’ve allowed yourself to get close with but two things pop in my mind that are very big building blocks of this topic.
1. “You need to love yourself before you can love someone else.”
It is very okay to not be 100% confident with yourself as long as you aim to eventually get there. It is a constant struggle everybody experiences. But it does very much interfere with getting close with people if you are insecure with yourself. Insecurities ruin everything. Your perception is your reality so if you have many insecurities, the more things will bother you. When it comes to a relationship, insecurities make you go on defensive mood since you might constantly feel peoples’ words/actions are threatening you. Unstable people are often more focus on themselves anyways since they are trying to find anyway to comfort themselves. That is not something ideal for a relationship.
Being single is not a bad thing; it gives you time to build the relationship with yourself and learn/understand yourself 🙂
2. Are the guys you are getting close with respect you?
Deep down inside you are probably a good person, most people are. But if the people, especially guy(s) you are interested in, do not view you that way, their opinions are going to rub off onto you the more you stick with them. So if #2 is the case, I want you to really think, the way your family/close friends treat you is it similarly to how these guy(s) treat you? Ideally guy(s) you are interested in pursuing a relationship with should not just be boyfriend quality but friend quality first.

I hope that has helped and made you feel better! If you add anymore detail I will try my best to respond to it if you would like 🙂 Best of luck!