The singer-turned-fashion mogul became engaged to former American football player Johnson in November, 2010, but she had to scrap two planned wedding dates after falling pregnant with son Ace less than five months after giving birth to her first child, daughter Maxwell, in May, 2012.
However, the new mum, who welcomed her little boy in June (13), has now confirmed she will tie the knot with Johnson this year (14) - and she cannot wait to wow her friends and family with her post-pregnancy weight loss.
In a new video advertisement for healthy eating firm Weight Watchers, the firm's spokesmodel says, "The new year will definitely bring on the wedding bells, which is exciting... I think it's about time.
"Knowing that I have the wedding coming up is an incentive to stay on Weight Watchers, count my points and stay in the gym. I mean, when you see my dress, you'll know."
And Simpson admits she is still working on building up her self-confidence, despite already stunning fans with her slim physique in recent weeks.
She adds, "I'm just trying to feel good in a pair of jeans and T-shirt. I can't wait to be able to feel just comfortable in my skin and know that I'm back to the person I've been before. I know this time I'm going to be so much stronger and so much more empowered, because I really earned it and I really got here, and took the steps to get here."
Simpson has declined to reveal a date and venue for her upcoming nuptials, but reports previously suggested she will wed Johnson in May (14) in Capri, Italy, where the blonde beauty spent her 30th birthday in 2010.
It will be her second marriage - she divorced singer Nick Lachey in 2006, while Johnson split from his ex-wife, stylist Keri Johnson, in May, 2010, after five years together.