Singer Rob Thomas has struggled to help his wife Marisol during her 14-year battle with Lyme disease.

The Matchbox Twenty frontman has been married to the brunette beauty for over 18 years and has been at her side as she battled the debilitating illness.

The experience has been a frightening one for the star who compares seeing his wife suffer to watching an alien inhabit her.

“It’s like if one day you woke up and there was an alien living in your house and the first couple of weeks you’d be f**king freaked out, but after a while you’d name it and it would just be there,” he tells Entertainment Tonight in a new interview. “This sickness has been like this weird alien that’s moved into our life and inhabited my wife. Sometimes she’s just not herself. Watching the person you’re closest to become someone other than herself is so (hard).”

The 41-year-old suffers from constant pain and seizures, due to the sometimes fatal disease, spread by ticks.

“It’s like you’re standing still, unable to participate as everything keeps going on without you, then you wake up the next day and the same thing happens,” she shares. “I don’t consider what I’m doing living. I’m existing... and fighting to hopefully one day live again.”

However, Marisol is grateful for the support of her husband, and feels terrible for other sufferers who don't have that kind of love.

Meanwhile, the illness has crushed the pair's hopes of having children together - something they have had to learn to accept.

“For so long now, we’ve told ourselves that we never really wanted kids together that we don’t know if that’s even true,” Rob admits. “We’ve known for the last decade that because of Mari’s health, that was something we couldn’t do and you just resign yourself to the fact.”

Thomas has also grappled with guilt over the fact that he’s healthy and his wife is not.

“Often their day-to-day life makes you feel selfish just by doing normal things,” he says. “l’ll say, ‘Man, I had the worst show', then realise who I’m talking to and go, ‘I’m sorry, that’s the stupidest thing to say!’"

Marisol is currently travelling with her husband on Matchbox Twenty’s A Brief History of Everything tour and working as an advocate to raise awareness about her illness, which also affects Avril Lavigne and Yolanda Hadid.