Hey there!

With 31634 rank in JEE mains, I don't think you will be able to get CSE or ECE in IITs for sure. However, in NITs , there's a chance. We can not surely predict about it but past trends will help you for sure. I would recommend you to try the Careers360's JEE Mains college prefictpr, as it will provide you great idea of colleges you can get into. Here's the link :-

https://engineering.careers360.com/jee-main-college-predictor?icn=jee-main-clgpd_landing-page&ici=prediction-section_c360-home

Hope it helps, thank your for asking question here. All the best!