Flexibility

Has anyone on here gone from stiff as a board to extremely flexible (I'm talking able to do the splits flexible)? Without going into too much detail I am trying to do this or get somewhere close, and it can be pretty discouraging so I was hoping for an uplifting testimony where this has happened. I have definitely gotten more flexible with how much I am stretching and doing hot yoga, but the tightness of my hips/lower back/hamstrings just doesn't seem like I will ever get to where I want to be. I have struggled my whole life with muscle imbalances and pulled muscles due to my naturally tightly-wound body. Once again, I am seeing a bit of progress but don't know if my body will ever let me get too much further. I have considered giving up my gym membership for a year and sticking with just hot yoga and stretching programs to get there, but I am hesitant because I love lifting weights and have seen so many tangible benefits from my gym work (Not to mention hot yoga is quite expensive). Any advice/suggestions/testimonies are more than welcome.