Sleep difficulties are extremely unfortunate because of how much they impact the rest of your life, and so I am sorry to hear that you are having trouble with this. Please don't stop exercising because of this! While you don't mention the timing of your exercise regime, it is possible that you are doing your intense physical activity right before you go to bed. This will cause you to feel extremely alert at a time when you should be winding down. For that reason, it is recommended to exercise at least a few hours before you try to go to sleep. Additionally, some of the energy drinks that are often used can obviously affect sleep.
If the only thing that has changed recently is you going to the gym, try going in the morning or early afternoon instead of the evening. Other possible changes include making sure not to go to bed hungry and not watching TV in the time right before you go to bed. While there are many things that can be done to improve your sleep hygiene, try these first. If you continue to experience difficulty, please speak to your primary care doctor
or a sleep specialist
, as there can be other causes for poor sleep as well, some of which are medically relevant.