It sounds like you express love through physical contact, emotional connection, feeling wanted and appreciated (all valid ways of giving and getting love) and that the boys don't. Maybe they feel love from you by providing a safe, stable house, a pat on the back, a word of encouragement, the room to play, the chance to "be boys."
I second stopping them and asking for a hug because it can really help you to feel loved, but if they are uncomfortable with it, then I caution that it would be unhealthy to push them into expressing love in a way that they aren't comfortable showing it. Just because they don't show love the same way you do doesn't mean they don't love or appreciate you. I'm sure you know that, but sometimes I need to be reminded so by telling you, I remind myself.
Brainstorm other ways to accomplish the same thing. Maybe your husband can give you a big hug and tell you how much he loves seeing you parent five boys as a means of showing appreciation? (Wouldn't hurt for him to model hugging for the boys, either.) Maybe the boys would enjoy learning hand clap games from you? Maybe you could bake cookies together? Start practicing "gimme five"s? Whatever ways you can physically connect while staying in their comfort zone.
And don't underestimate the power of one-on-one time. Choose a boy to take to the store with you and be your list holder, crossing off items. Let him choose the music in the car, sing silly songs, let him choose a treat (for himself if the other boys will go soon, or for all the boys if it will be awhile before they can go). Take the time to casually mention how much you love spending time with him and how great he is. He'll probably look back on it with fondness 20 yrs from now, feeling love and loved from the time with you.
And hopefully, you will, too.