I do so feel your fatigue. When easy child was a baby, I was a stay at home mom until she was almost 3 years old. I also had no one to leave her with whenever I needed. There were times when husband came home that I did say, "I am glad you are home. She is yours for now, I will be home shortly." I just needed a break and can't but imagine that your chances are so much less than mine? My husband is on the road a lot so there were weeks I did feel like a single mom with no end in sight. I can't see signatures in while replying. Did I see that there is a boyfriend? How is he with your son?
When I started looking for day care, I had one lady say, "Just stay home and do day care like I did!" I thought, "You don't know me, if I was willing to stay home 24/7, I would." I interviewed for one job that asked what I did for stress relief. I honestly answered, "Go to Work". I have never in my life ever experienced the not-able-to-handle-this-stress as I do as a mom.
Keep posting, we will do our best to help you through.