I am kinda new to the stretching involved in yoga. I thought I would stretch my legs out like crazy beforehand in order to develop extra flexibility. But now I think I overdid it. My hamstrings in particular feel sore and actually quite a bit less flexible than they did before. Is this normal? Thanks for the info 
Ah to be kinda new.
Since the poses (asanas) are what you ask about I’ll respond to you in kind. However, bear in mind that asana is one tiny sliver in a larger tree called Yoga.
In the marketing of asana in this country we’ve been deceived into believing that it is about suppleness, and flexibility. This is simply not so. There is a strong difference between contortionism (a completely mobile state) and asana.
Asana is about moving some things and stabilizing other things. Therefore if a student has desire to prepare for the preparing they would have to stabilize and mobilize. The body has a specific range of motion for a reason. That reason is, primarily, safety. Work to increase range of motion should be done gradually and with great care.
Frankly speaking, there’s no need to stretch before stretching just as there is no need to lift weights before lifting weights or run before running.
Namaste and welcome.
Well, that’s why there is a teacher in the class, to safely take you through the stretches and warming up prior to the class, not true?
Normal? Hope not. Definitely possible, though. Especially if you didn’t know you could hurt yourself by ‘stretching out like crazy’. Please notice that more stretching right away is not the key to help something that was hurt by being stretched. (not that I know for sure that this is what happened – but mentioning it might be helpful for you.)
You might also be suspicious of doing anything you will describe later on as ‘like crazy’. (I am giggling a bit as I type.)
Welcome to the forums, and I hope you find your ahimsa!
hamstrings can be likened to an ass/donkey ,the harder you pull in one direction the harder they tend to pull back,rather offer a carrott and gently coax them forward as the above poster suggests be kind and mindful of yourself.
good wishes to you
Many good comments above. I’d like to share my own experience.
Being a naturally flexible yogini, and one who’s ten years into her practice, my recent big discovery in yoga is that the absence of sensation results in the possibility of boredom, and also danger. Over the past few years, I reached such a place with my practice, and now feel “lost” in many standing poses. (When the sensation is absent, the trick is to fiercely work the mindfulness of the pose with strict alignment integrity. Consequently, I have retired from my advanced asana practice and enrolled in yoga rehab as a result.)
It’s quite natural to be sore from stretching out those muscle fibers that were bound up from tightness. By appropriately resting and returning to your practice, to the place where you meet the resistance and then breathe your way through it–that is the stuff of a rewarding yoga practice. Look at it as information, “grist for the mill,” and breathe through!