Are you really stretching your hamstring when you think you are? Most people put their leg up on something with a straight knee and pull their foot back (if they can reach it) with their hand. They usually feel a dull stretching pain behind the knee and/or up and down the leg. This is really a great neural (or sciatic) stretch. The hamstring gets a slight stretch in this way but it is not how to stretch your hamstring muscle.
Looking for a more muscular stretch feel most of us will then rotate our bodies away from the leg and get more of a stretch up the inside aspect of the leg. This now becomes a groin or adductor muscle stretch. It’s a good stretch but again it’s not the way to stretch your hamstring.

To do it properly you should put your foot up on something low like a chair, have your body facing directly down the line of the leg and point your foot forward. You should keep your back straight by sticking your backside out a bit and lean over your knee. The most important thing of all is to keep your knee slightly bent just like CJ is doing in the picture.

Example of a true hamstring stretch. Knee bent back straight and foot pointed.

Remember when you are stretching that you don’t need to be the most flexible person around you just need to be flexible enough to comfortably do the things you want to do. Push into a firm stretch that should feel pleasant and not painful.