Prenatal support

I am extremely frustrated with my child’s father. I had an ultrasound bill cost $500 and he promised to pay it. After 2 months of begging him for money for the bill he finally gives me $50 but promised me $100. He recently got a truck driving job making $700 a week and he gave me $50. So he called me and asked me for $100 because he spent his advance for a job and couldn’t put fuel in the truck. He promised to send it back the same day after he got paid plus another $50 for the bill. I was planning to pay the bill and buy some other things for my daughter with the money I sent him. So fast forward to now he keeps playing with me about sending the money back. He’ll say he’s on his way to send it but he never sends it. I just don’t know what to do at this point. I’m 5 months pregnant and he’s really stressing me out when all he has to do is give me my money back. I couldn’t work the first 3 months of my pregnancy due to sickness and he barely helped me. I work so hard and all of my money goes to my daughter and savings and she’s not even born yet. It’s a slap in the face