The McBusted bassist - the only unmarried member of the band - and the 'Starry Eyed' singer are completely smitten with one another and friends are convinced it is only a matter of time before he pops the question.
A source told LOOK magazine: ''They must have talked about it. If Dougie was to ask, I'm almost certain Ellie's answer would be yes.
''Dougie's seen all of his friends get married and he'd surely love to do the same, for both of them it seems they've found 'the one'.''
Ellie has previously spoken about suffering from crippling anxiety attacks and low self-esteem and friends credit Dougie - who was treated in rehab for depression, alcoholism and substance abuse three years ago - for helping her conquer her problems.
A source said: ''Ellie's had a difficult time over the years, especially when it comes to believing in herself.
''Dougie completely changed that. There's something very special about someone who understands what you've been through and he makes her feel beautiful every single day.''
Ellie's friends say the blonde pop star seems more comfortable with Dougie than she ever did with her previous boyfriends - who include Skrillex and BBC Radio 1 DJ Greg James.
The source said: ''Ellie's really struggled with her self-esteem. With previous boyfriends, I always felt like she was putting on a show, trying to be a perfect showbiz couple.
''She never seemed to believe she was good enough to be loved.
''With Dougie, they're on the same wave length and just chill. She can hang out in her gym kit with no make-up on. He clearly adores her and she seems besotted with him.''