Brandon Clarke‘s fiancée Amber Lorraine is mourning his heartbreaking loss … revealing the two were preparing to get married before his sudden death last week.

Amber shared an emotional tribute to Instagram Sunday alongside a series of photos and a clip including Brandon getting down on one knee — admitting that the day he proposed was the happiest day of her life … and she has no idea how to move forward without him.

In the lengthy caption, Amber called Brandon her soulmate and opened up about the life they were building together … saying they were supposed to marry soon, start a family, and eventually live somewhere where they could be surrounded by animals and a garden.

She remembered the Memphis Grizzlies star as endlessly talented and deeply caring — praising everything from his music and gaming skills to the way he made her feel loved every day.

Amber also shared intimate memories from their relationship … including watching ‘Harry Potter’ together, cooking his favorite breakfast and dreaming about their future — ending by asking him to continue watching over her.