Jax Taylor is revealing the reason he went to an inpatient treatment center this summer … he says he knew something about him was off, and it turned out to be two major disorders.

The ‘Valley’ star says during his multi-week stay at a treatment facility he was diagnosed with Bipolar Disorder and PTSD.

Jax says he’s known something was wrong with him for a long time and was scared to find out what it may be when he checked into treatment in July … and he’s still processing his diagnosis.

TMZ broke the stories … Jax decided to seek treatment in July for mental health issues, and he left in August to film another season of “The Valley.” At the time, the exact mental health issues were unclear.

Jax says since he’s been home, he’s found a sense of peace … thanks in part to his son, Cruz. He’s been hitting the gym and spending time with his son when he’s not on set.

Still, he admits he’s scared for the future and is trying to be a better version of himself. He says he’s taking things a day at a time because … “Mental health is a lifelong battle of not letting it control you but rather you learning to control it.”

Since leaving treatment with his bipolar and PTSD diagnosis, Jax’s been hit with divorce papers from his ‘Valley’ costar Brittany Cartwright … getting served while filming their reality show.

Things looked pretty uncomfortable on set for Jax this week … as he tried his best to ignore Brittany and keep his distance.