Post covid weakness and tiredness can last upto 3-6 months.
Maintain a good intake of water and a diet high in protein.
Add eggs to your diet if vegetarian.
If pure vegetarian - add chana, nuts like almonds and walnuts, soy milk, pulses (dal), chia seeds, oats, paneer, tofu to your diet they all are good source of protein
Next Steps
Get your haemoglobin checked and if it's low further management of anemia can be done which can help with your tiredness.
Health Tips
Till than you can add a multivitamin tablet for it