"I'm left cherishing his memories and carrying out his legacy," Westerberg, also known by his stage name Manila Luzon, told PEOPLE on Thursday. "I was lucky enough to have time with him."
Still, he says, losing the fellow RuPaul's Drag Race contestant is a struggle.
"I'm hanging in there, but it's hard because I have to deal with more than just grieving someone so close," he says. "I have to deal with telling everyone all the information. We've been together for such a long time, so it's surreal because it just happened. At least I have a lot of support from friends and family, so that's good."
When Westerberg first met Ashley – also known by his stage name Sahara Davenport – at a local bar in his neighborhood, he instantly knew this was someone he'd be connected to for a long time.
"We just really hit it off," he says. "And when we both found out we were drag queens, it was such an enlightening moment. I was starting a relationship with someone who shared a passion for something I did. It was a lot of fun."
"Antoine and Sahara Davenport were really able to help me learn about drag," Westerberg says. "We really fed off each other. Together, we just clicked. We were both part of RuPaul's Drag Race, so we both got to go through this experience together."
Now, Westerberg relies on mementos to feel like Ashley is still here. Granted, some of which he even considers "superficial" – but special, nevertheless.
"She left me a whole bunch of shoes," Westerberg says, adding that there should be a museum devoted to Ashley's creations. "She would design these amazing outfits and have them made for her."
"I can say that my love for Toni Braxton is so much bigger because of my boyfriend," Westerberg says. "Sahara was always trying to sound like Toni Braxton."
Westerberg, who will participate in Drag Race's upcoming all-star competition, says because the season has already been filmed, "All the stuff that's going to be said will be said as if Sahara was still with us. It's going to be a little hard to watch, but it's kind of cool."
Logo network will air a tribute to Ashley on Friday with an all-day marathon of his season, in conjunction with Tweets from fans. Additionally, the first episode of RuPaul's All Stars Drag Race, airing Oct. 22, will be dedicated to the former contestant.
A private funeral for the star is scheduled for Oct. 12 or 13 at Snowden Funeral Home in Rockville, Maryland. And on Nov. 2, XL nightclub in New York City will host a public memorial with tribute performances by Ashley's industry friends.
At the end of the day, "We're all going to die," Westerberg says, "but [people] really want to pay a tribute to [Antoine] and the huge legacy he's leaving behind. As a drag performer, he rose to the top. He was on television and people fell in love with him. He was an amazing dancer and performer, and he was able to showcase that to the world."
He adds, "A lot of people care about him and will remember him for all of that. This is a celebration of his life."