If you scroll through my Instagram account or watch my YouTube videos, you might think I’m just “one of those girls” who’s always been fit and healthy. I have a whole lot of energy, can make you seriously sweat without any equipment, and look nice and toned. There’s no way I could be suffering from an invisible illness, right?

The symptoms started out pretty mild. Occasional headaches, constipation, fatigue, and more. At first, doctors just thought it was hormones. I was 11 years old and going through puberty, so all of these symptoms seemed “normal.”

It wasn’t until my hair was falling out and all the other symptoms worsened that doctors started to take it seriously. After several rounds of blood tests, I was finally diagnosed with autoimmune hypothyroidism, or Hashimoto’s thyroiditis.

Essentially, this is an inflammation of the thyroid caused in part by the body’s immune system. Symptoms include the ones mentioned above, along with a laundry list of others, like weight gain, struggling to lose weight, joint and muscle pain, severe dry skin, depression, and difficulty getting pregnant, just to name a few.

As a teenage girl, and later a college student, I ignored most of my symptoms. But my struggle with weight was always glaringly obvious (at least to me). It fluctuated up and down by 10 to 20 pounds every few months.

As you can imagine, this affected a lot of other areas of my life as well. By the time I graduated, I was the heaviest I’d ever been and feeling completely blah.

As my weight increased, so did my insecurities. I struggled with confidence and continued to use my condition as an excuse for how I was feeling, both inside and out.

I never once stopped to think about how the food I was putting into my body affected my illness. Doctors never really addressed this. It was more like, “Take this medication and feel better, OK?” But it wasn’t OK. I honestly never felt like my medication did much of anything, but again, I just assumed that was “normal.”

I started doing a lot of research, talking to new doctors, and learning how much food and exercise impacted my hormones, immune system, and overall functioning. I didn’t know if changing my eating habits would really help, but I figured it had to be better than the fast food and sugary drinks I was having on the regular.

Changing what I ate seemed like the best place to start. I loved cooking, so it was just about learning to get creative and make my less-than-healthy dishes healthier.

Working out was more of a struggle. I was always so tired. It was really hard to find the energy and motivation to exercise. Plus, I had a built-in excuse, so it was a lose-lose situation for a long time.

I made small changes, and eventually started adding regular exercise back into my routine. Nothing crazy like the insane programs I had tried and failed at in the past. I was walking, jogging, and making up workouts at home. Six months later, I had lost 45 pounds.

The weight loss was great! I was 23, single, and ready for a confidence boost, but it was more than that. For the first time in my life, I didn’t feel tired every day. I had more energy, wasn’t getting sick every few weeks, and wasn’t experiencing the same severity of symptoms as before.

Seven years ago, I decided to stop making excuses and start making myself a priority. Now, I’m a personal trainer, group fitness instructor, author of the “Hot Body Sweat Guide,” and the healthiest I’ve ever been.

That’s not to say I still don’t suffer from symptoms though. I do. Most people wouldn’t know it, but there are days I sleep nine hours and still feel indescribably exhausted. I actually still deal with a lot of the symptoms, just on a less intense scale.

But I also make a choice every day. I choose not to let my autoimmune hypothyroidism stop me from living my best life, and hope to inspire other women to do the same!

Katie Dunlop is the founder of Love Sweat Fitness. A certified personal trainer, group fitness instructor, and author, she’s committed to helping women achieve health and happiness. Connect with her on Facebook and Twitter!