Is it normal to feel fed up being a parent every day?

I am a single mother with absolutely zero support from family or friends so I'm with my son 24/7. He's 4 years old and stopped napping when he was 1 so it's 14 hour or 15 hour days I have none stop with him, no breaks and I find myself just getting fed up or agitated towards the end. I control my emotions and never let him sense or see how I'm feeling but I still let my mind wonder about how much easier it would be if my partner was here and if this is how everything is going to be forever as I've been single for 5 years now!!! I've not hugged or had any proper interaction with a guy since my ex husband (my sons father) and my ex now has a delusional girlfriend backing that he's an abuser and standing by him and she has 2 daughters from a previous relationship which he treats like shit but they've been together for 2 YEARS and post all happy professional photo shoot pictures all the damn time while I'm here. No child support, still divorced, having to save up for the divorce as he didn't get the divorce done himself 2 years ago when I asked him too cause his actions say he wants to stay married. I've got all this going on and the thought of even imagining having another boyfriend in the future isn't something I can honestly see happening. I've never dated while being a single parent and I can't imagine many men will want someone who's got a kid, it still legally married and isn't psycho. So for me in my head I've accepted I'll be alone , forever. Its the most depressing feeling in the world that my ex is a family to someone else's girls while his son is in another country in the UK with me ( my ex lives in the US) and I'm here picking up the pieces from our marriage. He wanted to have a kid it was his idea not mine but he convinced me that I wouldn't get pregnant straight away and we should see what happens by just not taking the pill and sure enough less than a week later we conceived. I wanted to wait and work and sort out my visa in America while I was living with him but he got abusive and forced my by that to leave with his actions but calls ME the selfish one, saying I brought this life style on myself for being selfish and leaving. I did everything for him, cooked , cleaned literally everything and I got nothing.