The couple's careers are getting in the way of their romance

Justin Bieber and Selena Gomez may be about to end their 18-month relationship.

The teen couple are said to be struggling to maintain their romance because of their busy work schedules and have broken up ‘multiple times’ over the past couple of months.

‘They might be young, but Justin and Selena‘s is a very adult relationship,’ says a source.

‘They have had to grow up really fast because of the pressures of their careers.

‘To begin with, their similar situations complemented each other, but now they seem to be drifting apart.’

Justin, 18, has been away from home a lot over the past few weeks as he promotes his new album Believe in Europe and he recently announced a 6-date UK 2013 tour.

The singer made a last ditch attempt at showing Selena, 19, how much he cares by waiting for her at an airport when she visited him in his home country of Canada last month.

‘It’s unusual for Justin to put himself on public display by doing something like waiting at an airport arrivals area because he knows he’ll get mobbed,’ the source tells The Mirror.

‘But things have been so patchy with Selena lately, he needed to make the effort.’

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Anna Duff