1) Islam has given us a lot of advice on mental health. Some examples:
A- Working on oneself to avoid these vices: greed, jealousy, arrogance, etc… It has shared practical steps to avoid such vices. Avoiding them helps improve our mental health.
B- Not to think about the future too much and worry about the future. The future is in the hands of Allah. We have reliance on him.
C- Doing sujud and saying Subhana rabbial a’la wa behamdeh (for several minutes at least). Or saying la ilaha illa Allah regularly (such as 100 times a day).
D- Avoiding too much stress or exhaustion.
E- Crying
F- Sponsoring orphans and visiting the sick
G- Eating foods that have a good impact on the intellect and soul, such as quince or squash/pumpkin.
2) Regarding OCD, it is healthy to be meticulous about Fiqhi rulings, but of course it should not be excessive. Whenever you find that it becomes excessive, we are told by the Imams to ignore our doubts. Also, the following Du’as / procedures help with OCD:
A- Wash your head with Sidr water
B- Read these Du’as:
آمنت بالله وبرسوله مخلصاً له الدين
هو الأوّل والآخر والظاهر والباطن وهو بكلّ شيء عليم
توكّلت على الحيّ الذي لا يموت والحمد لله الذي لم يتّخذ ولداّ ولم يكن له شريك في الملك ولم يكن له وليّ من الذلّ وكبّره تكبيراً
لا إله إلّا الله محمّد رسول الله عليّ أمير المؤمنين
أعوذ بالله القويّ من الشيطان الغوي وأعوذ بمحمّد صلى الله عليه وآله الرضي من شرّ ما قدر وقضي وأعوذ باله الناس من شرّ الجنّة والناس أجمعين
This should be effective in helping you with this situation Insha’Allah