Getting asleep immediately after dinner.

Greetings I usually get fully exhausted and asleep immediately after taking dinner. Hardly I stay awake for 30 minutes and after that forcefully my eyes get close and I am forced to lay down on the bed. Even if I am holding a TV remote it will fell down from my hand unnoticed. I feel this problem even worst if I sit on computer screen or mobile screen immediately after dinner. My cursurer get uncontrolled and it get clicked haphazardly. My digestion looks normal and moderately I have gasses released while moving and bending over. Stool test is normal. I have dust allergy and consequently allergic rhinitis accomp within I am 61 years male, diabetic since last 25 years hypertensive and have hypo thyroidism. Currently taking following medicines : BEFORE BREAKFAST DIAMICRON MR 30mg 4 tablets  Thyroxine 50mcg Cozaar 50 mg Glucophage 750 XR each after breakfast and after dinner. Januvia 100mg after dinner LIPITOR 10mg after dinner Methycobalmin Tab twice a day Please assist me