Constipation and medicine issues :( help!

So my son who is 3 is having a lot of problems with eating lately. He gags, chokes and throws up when eating. His special need preschool thinks he could have a sensory processing disorder but they lost their OT over the summer and havent hired a new one yet. Meanwhile his issues have gotten worse. Now since he doesn't want to eat a lot, he's been getting really constipated. It's the third week of him onling once a week. I've tried medicine but because of his texture issues he can't stand medicine. I've tried hiding it in yogurt, applesauce, sugar water, he just flips out going nuts.   I dont know what tp do. Please help

can he eat chewables ? if so try pepo im not good at spelling but it comes in a pink box it use be liquid now they got chewables it taste like candy my daugther said

pepto for childrens

or if he likes apple juice try that dont add water. .i hope u find something that works . .