Am I in the wrong ?

I hate how my "bestfriend" makes me feel like a crappy friend because I cant just get up and go do fun things with her at any time of the day (shes pregnant with her first and her boyfriends working out of town currently). I'm pregannt with my second and have a 16 month old, I dont ever have anyone offering to babysit except my grandma and she cant babysit all the time every single time I want to go have fun. I constantly tell her to let me know in advance so I can ask my grandma in advance and pay her but instead she let's me know literally that minute and then makes me feel like a horrible friend when I say I cant go. She says "your always just staying home, when I have my baby I'm not going to be like that I'm still going to go out with friends etc and I'm going to show you its not that hard" cause all of her family is already offering to babysit, sorry I don't have the same support. Then she says things like "bring your baby with you " to go swimming and stuff, like do you know how hard it is to be 24 weeks pregnant and chase after a 27 pound toddler in 100 degree weather ??? Shes the type of friend who never offers to help with him she goes and has her fun while I'm struggling chasing after my son which I dont mind because hes my son it's not her responsibility but you would think if she wanted me to bring him that she would help play with him and swim with him so I can enjoy the day to?? Idk maybe I'm pregnant and over reacting but she makes me feel like shit when she post stuff like how she posted today she went to hang out with another girl because I couldnt go swimming with her last minute cause I didnt have a sitter and she put ",thank you for being here for me while my boyfriend away, your a good friend" and tagged her in it. I'm so over it, and so over feeling like a horrible friend because I cant go have fun every single day. It's so easy for her to do things because shes pregnant and can just up and do things. I even tell her let's go to the aquarium or something that's fun for my son and she says no that's boring etc etc. Am I in the wrong ?? Am I being a bad friend for not being there for her while her boyfriend is gone ??