I am 16 years old and I am not such a bad Muslim in terms of knowledge, there's just two things, I am too lazy and don't go to the Masjid even when its only a 2 minutes walk away, I get distracted easily, and only recently I have started to miss some Salaah completely on purpose.
The Second thing is that I keep on doing a 'certain' sin, to satisfy my lust. And don't know how to resist.
I have made Tawbah, and constantly asked Allah for guidance, some times I suddenly feel a big boost in Imaan, but the next day I'm back to my sinful ways.

It Never used to be like this what happened? A year ago I was a better Muslim, never missing salaah on purpose also going to the masjid and not doing this 'certain' Sin. I fear Allah plz help

Jazakallah, inshallah allah rewards you all.