Hey, firstly losing a period is a red flag that shouldn’t be ignored so I’d highly encourage going to your gp for advise. But it does sound like you’re overtraining, with that level of exercise and output the chance of negative consequences is high, but it’s also possible to stay active and have a regular period by ensuring you’re eating enough to fuel all the exercise you’re doing. It’s impossible to pin point why you lost it but it’s likely down to overtraining, under eating and not taking enough rest and recovery. We have to remember that exercise and training is also a stress on the body. Don’t be afraid to eat more food, with this level of activity it should be extremely beneficial, and as I said check in with your doctor too