"I feel good, but I don't have the energy I used to have," El Moussa, 34, tells PEOPLE. "The only thing is most days or like half the time I feel a little jetlagged. I'm really tired."
The real estate guru, who stars alongside his wife Christina on their hit HGTV show, was blindsided by the shocking diagnosis after a fan emailed producers saying she noticed a lump on his neck prompting him to have a biopsy.
After surgery revealed it was in fact cancer and it had spread to his lymph nodes, El Moussa then underwent thyroid radioactive iodine therapy.
"The last three years have been a pretty big challenge," says El Moussa.
The couple, who are already parents to daughter Taylor, tried for more than two years to get pregnant with their son, going through two failed attempts at IVF – including one resulting in a miscarriage at eight weeks, just before Tarek’s diagnosis.
Now in remission, the new dad, who welcomed son Brayden James with Christina, 32, in August, is positive about his family's future.
"There is always that chance of reoccurrence but every year that goes by the odds of reoccurrence goes down so it's good," he says. "I have slowed down quite a bit. Which is actually a good thing because I can actually relax now."
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Flip or Flop airs Thursdays (9 p.m. ET) on HGTV.
For more on the El Moussa family, pick up next week's issue of PEOPLE, on newsstands Nov. 23