Overwhelming my girlfriend

I am feeling as if my girl is not interested in me anymore. We have been together for some months now and I thought things were ok. I have a 2 year old child. I have him on some weekends. I work during the week and so does she. I only am able to spend time with her when I don’t have me child. So we spend about a couple times a month with each other. She is understanding the best that she can. There are so many events I missing out with her because I have my child. She sometimes knows it’s a weekend I will have him and she just cancels the plans and stays in at home by herself or she goes on a solo date. When we are together on my free weekends she is at my house and we just chill. She stays the night and leaves early afternoon the next day. So I think we spend maybe 24 hours together. I can see that it gets to her that I can’t do much with her. I’ve missed out on so so much. She spends alot of time alone. When I have my child she doesn’t call she lets me reach out to her and I’m appreciative of it. I feel bad now that I see that when we do spend the time together, I don’t take it seriously. We watch tv on the couch and chill. We don’t go anywhere, next day she is dropped back home early afternoon. Now I noticed how down she sounds with me on the phone. She not talkative. She goes to do things alone now. I guess I just need to know how can I capitalize on our limited time. I did use to stop by during the week but I’ve stopped it slipped my mind.