Is Miralax safe for a long period?

Hello doctor,

I wanted to know whether Polyethylene glycol 3350 (Miralax) is safe on a long run? I am having it for the last 25 days. Is it safe enough? I have a constipation problem and visited many gastroenterologists and tried many laxatives, but only Polyethylene glycol 3350 gave me relief. But from the past three days, I am having severe stomach pain. Now, I have started the Mebeverine hydrochloride capsules as per the doctor's advice for stomach pain. I want to know the cause of this severe stomach pain. Is it due to the usage of Polyethylene glycol 3350 (Miralax) that I am taking from the last 25 days? Is Mebeverine hydrochloride fine for the stomach pain that I am facing? The other medicines that I am taking include Nexpro RD (Esomeprazole and Domperidone). Recently, I had got all blood tests done. Previously, I have undergone an endoscopy twice about four years back and once in last year. I had got an endoscopy done because of stomach pain problem and gastritis (GERD) was found.

Thank you doctor,

I had undergone ultrasound scan two times. I had undergone one about three years ago and the other ultrasound scan was done about two years back. My question is whether Miralax is safe for a long period?