Yaar don't stress too much about strict fasting because your health is super important for conceiving. If you want, just do a light puja or simple prayer to keep your mind positive and stress-free.
Santoshi Maa vrat or Solah Somvar is considered very auspicious for this. Just keep your heart clean, stay positive, pray with pure devotion, and avoid starving yourself too much because physical health also matters.
People suggested me so many vrats but honestly, if I had fasted, my energy levels would have crashed completely. Trust your doctors and eat well, twins conceiving ho gaya toh waise hi dher saare vrat rakhne ke barabar mehnat karni padegi!
I felt so desperate to conceive at one point, so I kept the Solah Somvar vrat with full devotion. When I got my positive result, I literally couldn't stop crying in front of the mandir.