still not letting myself be happy

After 5 years of infertility, I'm 28 weeks pregnant. It's a dream come true, but I feel like I can't be 100% happy. I keep worrying something is wrong with the baby or that this is some sort of cosmic joke and something bad will happen. Is this normal? I feel my baby boy kicking and I'm reassured, but I keep having the same negative thoughts. Im even scared to do my baby clothes and gadget shopping. Anyone else feel this way?