First, I'm so sorry about the passing of your pup. It's so hard. People that don't have pets just don't understand the void they leave when they are gone. Hugs to you and your boyfriend.
I think some people feel "guilty" about getting another dog "too soon", but for me, it isn't about replacing the one you loved, but rather sharing the love. You gave an adult dog a wonderful life, and it's never too soon to do that for another!! When my beloved dog died a few years ago, I already two other dogs, so while I certainly grieved (and can still get misty eyed when I think of her), my other two dogs helped me through it. If you feel ready, you are ready. There is no right time.
My bff got a puppy two days after her dog died at age 14. It was the right decision for her. She was a single mom, young girls, and seeing someone walk their dog down the street had her sobbing. The new fur baby didn't make her less sad about her fur baby passing, but did help her through the grieving process.
So many dogs need homes, and I think it's awesome you want an adult dog. If you find one that speaks to your heart online, go meet him/her. If it's right, you will know.