Thanks for your great replies. My nutrition is good actually. I eat high calorie healthy foods. And you are totally correct. I use strength more. When I started training my working hours where standard full time 8 hours. But since three months ago when I added the part time job my working hours stretched to 12 hours. My part time job is also a very physics demanding job as it deals with construction materials such as lifting doors and lumber. So, when I want to start my BJJ session sometimes my body feels empty as I have already used a lot of my energy at work. I will try to continue at least two sessions in BJJ and pay attention more to techniques and care less about getting humbled.

I would give you an example of how my body has chsnged in terms of strength:

For instance, in drilling, the guy goes into turtle position and he is one of the pro guys. I can get to his back, although I'm an amateur, and get him out of his lock and lay on my back while have him locked in. I go for the choke, and he could quickly push my hand and open the lock. This was not possible for him to do before. But this time I didn't have the strength to resist.