Feeling Fatigued too soon. Or smoke.

Hi, I am 35 YO Male and recently started suffering from fatigue, I felt some tiredness throughout the day earlier as well but for the past 1-2 weeks it has intensified that despite taking a light meal and a good nights rest, i feel lethargic, more so after a meal. I think it could be due to the redundant lifestyle during pandemic and work from home culture. Living like a couch potato. Thinking of trying a multi-vitamin for the same. Please recommend something that will help. Have tried A2Z and Revital in the past but without any significant improvement. Please recommend something gentle for the stomach as I suffer from occasional constipation and have Allergic Rhinitis (lot of sneezing) too for which I take Duonase spray, once every 2 days but sneezing is still there. I am Vegan and don't drink or smoke. Thank you in advance.