Before you call it quits on a med that's working, try a fiber supplement called Daily Fiber Formula by Yerba Prima. You can find it in any health food store. And analyze your diet. Is there enough fiber? Too much sugar? Too much white flour? Too much red meat? Try to work with the Lexapro, because finding something that works is very hard. Also keep in mind you're still on a very low dose. 5mg works for some, but the lowest therapeutic dose is 10mg. It may sound odd, but sometimes too low a dose can cause the side effects of beginning of a new med to hang around. On the other hand, increasing can cause it to worsen, too. It's a crapshoot. As for your doctor telling you constipation isn't a side effect, you might want to find another. I find that when a psychiatrist tells you nonsense, what happens when you really need him or her, such as when you want to discontinue the med? Of course constipation is a possible side effect. As is diarrhea. Keep in mind that most of the serotonin in your body is in your digestive tract, not your brain, so all antidepressants can cause digestive problems of all kinds. Good luck.
try eating some nuts, raisins, and/or fiber cereal. drink lots of water. give that a chance. otherwise don't stop the Lexapro all at once, you must reduce gradually or it can mess you up.