Check your calories. I do 3.5 hours per week cardio and on 1200 calories a day I would quite literally waste away.

You must be eating more than that. Way more.

twice a week I do 1600 ..... I mentioned that

How did you decide on how many calories to eat?
It sounds kind of arbitrary. I mean, it sounds like it's worked for you overall, so it's probably not unhealthy, but it might not be as effective as it could.

That's why I suggested the lean mass/body fat percent calculation. It would give you a good idea of how many calories you actually need.

Anyway, really just curious, not trying to be pushy or anything.

Just A combination of various sites with the weight-loss calculators on them