ANSWER:

The more you get closer to Allah, the more satan is frustrated and tries to depress you and intimidate you so that he would hinder your journey to Allah and distract you if possible.

Ignore such feelings and feel positive and motivate yourself by looking at the beautiful things that Allah has given you so that you can be positive and grateful to Allah.

I pray tahajjud,Dhuha, all Sunnah and Fard prayers on time, I fast Dawood Fast, sometimes monday and thursday instead, and fast white days. I avoid major sins completely and try hardest to avoid minors. I wear hijab and am polite with people, Alhmadulilah. But sometimes I feel tightness in chest and cry or feel very sad and heavy for no reason. I find it hard to study etc, can you give advice pls