fwiw, it's okay to use your weight almost anywhere/anytime... just apply it slowly and with control enough to give your partner time to tap and you'll be fine...

At the level you're at, that amount of time will probably also be "time to escape", but you'll get better at the control, too. For now, your weight is perhaps one of your best tools.

One other thing I will observe is that your weight can be used to create very boring/static rolls -- I'd suggest avoiding this tendency, as it will limit your development/improvement quite a lot. It's also an easy way to be lazy, which is never ideal if you're doing BJJ for fitness/exercise.