Brian Austin Green has been battling Ulcerative colitis over recent weeks.
The 48-year-old actor has explained his recent absence from Instagram by highlighting his health struggles.
He said in a video message: "I disappeared from Instagram for a while. I had Ulcerative colitis for about six, six and a half weeks, which wasn’t very fun. Horrible timing. Horrible timing."
Ulcerative colitis is an inflammatory bowel disease, and Brian revealed he's been bedridden over recent weeks.
However, he's also heaped praise on his girlfriend, Sharna Burgess, who has taken care of the actor and his sons amid his health issues.
Brian - who has Kassius, 20, with Vanessa Marcil, as well as Noah, nine, Bodhi, eight, and Journey, five, with Megan Fox - said: "Sharna was amazing. Six, seven months pregnant, taking care of my three young kids, cause I was pretty bedridden for a while."
Brian admitted he's lucky to have someone like Sharna in his life.
He explained: "Taking care of me. Not complaining, being amazing. I am super thankful to have someone like her in my life."
Earlier this year, the loved-up couple announced that Sharna is expecting a baby boy "on or around" July 4.
Alongside a photo of Sharna's baby bump, the 'Beverly Hills, 90210' star wrote on Instagram: "We want to thank everyone for the amazingly kind well wishes [heart emoji] we are really excited to be welcoming a baby boy on or around the 4th of July :))
"@sharnaburgess, I cannot wait to see you hold your/our baby (sic)"
The actor is also "excited" to become a dad again.
A source said at the time: "Brian never expected to be a dad again. He is excited. Sharna makes him very happy. Their relationship is fun."