Check with your doctor or pharmacist regarding the medicines you are on and have them explain the common side effects. Stool softeners are safe for daily use if approved by your doctor but using a laxative daily can worsen constipation.
I am 60 years old female and I am taking chemotherapy that is constipating me, which I usually don't have that, not since I was much younger. Anyhow, I had to do SOMEthing. Since you are a vegetarian, you might like this idea, it works like a charm for me. I like canned spinach, always have, with a little salt. Now, I eat it right out of the can, I don't mind, and I salt as I go. A half can of spinach, and my digestion comes out like it's supposed to. It's not perfect, mind you, but it most defnitely keeps me from having constipation, and if anything it's a tad watery. I'm sure you could heat a half can in a bowl in the microwave the make it taste better. And I, too, am a big water fan, but it took "straight spinach" to keep me normal.
I might add that it just looks to me like the medicines you take, there ought to be some kinds that will benefit you the same way but not cause constipation, but I have to assume you have addressed all this with the prescribing doc already. But wanted to mention it just in case. My cancer doc also suggested I try this tea, it's called something like "Smooth Moving" something or other, and I haven't found it yet in the regular store, so will have to keep looking, so there's another possible easy remedy. I also find that salads help my digestion, but not necessarily in the face of constipation.
Now, I have a relative who is older than me, and she has to take iron pills, which can constipate, so she takes a stool softener with the pill, and it keeps her out of trouble. That's pretty mild stuff, I remember using it one time for a while, so that might work, too. Those would be what I know on the issue. By the way, if you haven't gone in four days, and you know it's right there and ready to come out, then in order to jump-start your anti-constipation regime, pick up some PediaLax or BabyLax at the pharmacy, it's a very small box with a bunch of tubes of ointment in there, squirt a couple in your rear and it'll come out in minutes in a big hurry. Repeat if you need to. That way you can start fresh.