"It's very surreal and humbling and crazy rare," JP, 42, said in a series of Instagram Stories videos from his hospital bed.
JP is married with children to Ashley Hebert, who starred on The Bachelorette's seventh season and accepted a marriage proposal from JP on the 2011 finale.
"Things you do every day, like picking up this phone or buttoning buttons and tying shoe laces, putting on deodorant, you just can't do it," JP continued in his videos.
"Picking up my kids? Can't do it. Wiping your ass? Well, that may be T.M.I., but I might have Ashley assist on the next one."
According to WebMD.com, Guillain-Barre syndrome can cause muscle weakness, reflex loss, and numbness or tingling in parts of the body. While it can lead to paralysis and permanent nerve damage, most people tend to recover, even those with severe cases.
People with the condition, which reportedly affects about one in 100,000 people a year, typically need to be hospitalized for days or weeks.
"I just can't really believe it," JP said in his set of Instagram videos, adding that "a lot of physical therapy" is going to be in his future.
Doctors, however, will continue monitoring JP in the hospital for at least a couple more days.
"I've heard from a lot of people and I know that things can get a lot, lot worse, and so -- knock on wood -- hopefully that is not the case for me," JP said.
"Hopefully I'm fortunate enough where we caught it early enough, to start a treatment early enough where we can now start recovery. But I will know more [on Monday] once I speak with the doctor."
JP, who has two children with wife Ashley, went on to thank his fans and followers for their "advice, guidance, support, and love."
"It's super heartwarming," JP said, explaining that friends, family and total strangers have reached out to him with support and information about the rare condition.
"It's just really nice, so thank you from the bottom of my heart. I've come this far, I will certainly keep everybody posted on my progression."
"Hopefully I wake up tomorrow and the symptoms are again, no worse, hopefully better -- at the very least, the same. I'll keep everyone updated on when I can get out of here and start getting back to some normalcy. Love you guys, thanks."
Ashley shared the scary news with her own followers Sunday on Instagram.
"JP was diagnosed with Guillain-Barre syndrome yesterday," she wrote in Instagram Stories.
"He is in treatment and doing well. It may be a long road to recovery, but we are so grateful to everyone that has helped us get to a speedy diagnosis and treatment. Thank you to everyone that has reached out."
JP and Ashley fell in love on The Bachelorette and then got married in December 2012 in a ceremony that aired on ABC and was officiated by franchise host Chris Harrison.
The couple -- who are parents to son Fordham Rhys, 5, and daughter Essex Reese, 3 -- renewed their wedding vows in Aruba in August 2018.
Just last week, JP posted a sweet message to his wife on Instagram, wishing her another happy wedding anniversary.
"7 years down, probably about 3-4 more to go," JP captioned a family photo.
"Happy anniversary to the woman responsible for all the love and happiness in this picture (and basically all my pictures for the last 7 years). [Love] u @ashleylynnrosenbaum."