Get a thermometer you know is accurate (Reli-On ones are cheap at the store, about $5). The minute you wake up, before you move, take your temp. Are you above 97? Then at about 2 or 3PM, take it again. Have you reached 98.x? If the answer is 'No' to both, get your thyroid checked.
I was the same way and did some investigating. I came across this:
Worked for me. People will tell you all day long that modern Western country's have plenty of iodine... I say "where"? I don't eat fish/kelp and used to use Sea Salt only sparingly. Avoiding all salt because of blood pressure is also recommended by docs...if those people don't eat fish/kelp, where is the iodine coming from? 150mcg from a multi isn't a lot when deficient. It's not in Milk or Bread anymore either.
I'm irresponsible, I just bought some IOPlus 12.5mg iodine/selenium tabs, quartered them, and took one on Mon, Wed, and Fri. Don't do that, go see a medical professional... after you read that thread
At the very least, a thermometer is a super cheap way to rule out thyroid issues.
There could be dozens of reasons you're feeling tired. I would definitely seek medical advice if it continues for a few more weeks as it could be something more going on inside that is making you tired. How is quality of sleep? Don't let it go on for too much longer though without seeing someone OP. You never know what's going on without getting checked out.
Self diagnosis and prescription are probably not the way to go. Ideally you'd go get a blood test and see if anything comes up. If you aren't stressed, get plenty of sleep, and take in proper micro and macro nutrients... it's time to see a physician.
If you are lifting heavier weight it will naturally make you more tired on top of that you are bulking. The meals you are eating if not spaced properly could be taxing your body even further. Space apart your meals, avoid stims past noon and keep getting your 8 hours in. What else has changed for you in the past few weeks?
As stated above i would really recommend a cbp test, that does NOT show your test and estro levels though you have to ask the doc or nurse for that test separate. If your panel comes back fine the next thing i would think of is sleep and solid sleep not in and out. Also make sure you are getting the proper micro and macro nutrients. In the cbp test it will show your micros and see if you are deficient in anything.