Being tired the next day after working out.?

after taking SuperPump 250(a nitric oxide supplement with Creatine) I do my weight lifting workout, plus I do a ab work out everyday (don't know if it matters). After, I drink a protein shake. Then 30 minutes later I eat dinner. I usually eat chicken, tuna (fish), veggies, a lot of water ( a gallon a day). in the morning I eat 5 egg whites with olive oil, whole grain cereal,(or oat meal), 1 or 2 pieces of fruit, a protein shake, and a multi vitamin. Lunch I eat a salad with grilled chicken low fat dressing. But heres where the problem incurs... I get off work and I go home and I am so tired for some reason that I go right to bed sometimes sleeping 6 to 7 hours. My loved one is becoming concerned about how much i sleep and wants to know why I am so tired. I tell her I just stated working out and weight lifting for the 1st time in a long time and my body is getting use to it and needs sleep to repair. Am I right? or is it my diet or maybe its the supplements I am taking (she thinks its the superpump 250 thats making me so drained and tied) I only take it on the days i work out. I work out for 3 days and rest a day. can someone tell me why i am so tired after i work? I am a manager at a fast food joint so its not to much physical labor.