Baby pukes a lot

My preemie was prescribed NeoSure two times a day. But every time I feed her that she pukes when being laid down. I make sure i burp her and to wait at least an hour before I lay her down and she still pukes all over herself. I’m so scared she’s going to aspirate. Breast milk doesn’t make her puke and she hardly burps with it. It’s just this formula. We gave her Enfamil Neuropro before we got the Simlac NeoSure and she seemed better with that one.