It has been too long again, and I really need to vent!!

I have not been on here in sooo long, it seems unreal. But I guess when things are going well, why bother right? Wrong. I should try to come on here at least once a week. I need someone to talk to even if no one replies.
Anyway, I cannot catch up with everything, however lately I've been feeling like I AM ALL ALONE, FOR REAL!! Like everyone I know and don't, is living without thinking about me... I am not sure if this is a good thing. Well, what I mean is, for example, my Best Friend does things without thinking about inviting me, why? I don't know. We used to do things together but now we don't. I invite her but she does not invite me. She is dating and I am not, so does that matter? Idk, howeve if she has a problem she calls or she calls to just talk but leaves out that she is "doing stuff or going somewhere". At first I thought I was just jealous, now I realize that I am lonely, miserably.
And this is not just my BF, my sisters and anyone else I can think about. I am not living and it is alright with everyone else. I have never been so alone in all of my life. My mother is not here (deceased) and I feel like I cannot "get over it".
Also, my children's life is suffering because of it as well.  I need to improve myself but do not know how. I am sad most of the time and trying to fake like I am not, I HATE MAN MADE HOLIDAYS LIKE VALENTINE AND MOTHER'S DAY AND HOLIDAYS FOR FAMILY AND FRIENDS.  I feel like I want to leave( not death) just move, why bother to tell anyone, F- off to everyone.
I had plans for this summer, my favorite season with my sisters, cousin and BF, but I canceled. I don't feel like being fake for "this weekend" with people that will not bother to call me for "a weekend". I realize that I am being petty, but I am hurt.
Another thing is I am the only single( except my little sister), but she lives in Maryland, so she does not count most of the time. So does this matter? I am not sure....
Updates:
I am working, I am in school online, I am still single, I am not taking meds for BP( maybe should, lol), I am getting along with my Ex(for the moment), I am just raising my youngest two children(the oldest is living w/ EX) and I am working at trying to be a happier person( a lie, I have not done anything different, idk)