Has anyone ever experienced this with their newborn?

My son is a preemie (35w 5d). He made his month a few days ago. Everything was normal. He had no trouble pooping like 3-4tikes a day. Out of no where he’s only been able to poop with a suppository. I’ve used it for two days now and I don’t want to go for day 3 :( I don’t want to get his body used to it. He pushes and grunts all day but nothing comes out, just gas. I hate seeing him like this because he was so good about it for almost a while month. Does anyone have any advice? I’ve done all the bicycle kicks and what not but it stopped working. He’s too young for gripe water but I will ask his doctor on his next apt in a few days. I just want him to poop :( because when I add the suppository, it all comes out. And it’s all the same, mustardy yellow. It’s not hard or anything so I’m not sure why out of no where he just stopped being able to. I looked up possible medical conditions and freaked myself out but I keep telling myself there’s no way because he was doing perfectly fine! Any advice will help. Especially if you’ve been through this! Should I use another suppository or wait 3 more days u til his appointment. The suppository does say to not use more than a week.