Baby not burping

How can I get my almost 4 month old to burp? He’s not burping today but I can tell he’s having gas pains, he tenses up. And when his belly makes a popping sound he cries ☹️ I tried doing bicycles with his legs and a warm bath which helped him let out some farts lol but no burps. I tried burping him while he’s up against my chest, sitting up & across my legs. All with no luck