Should I listen to astronomy app ?

So me and my boyfriend have been together 3 years since we were 17 and I love him so much he's a Marine and my Sign is a cancer and he's a Virgo and we are so comparable our bond is so strong the love is even stronger we fight like cats and dogs but that doesn't mean anything we try going our separate ways and we still couldn't leave each other alone.. But back when he was in college he met this girl named Tia and she's a bit off.. Like u don't wanna be with me I'll kill myself off and she her and him were sleeping together for a while and then he stopped when I came back into the picture and Tia just so happens to be a cancer as well and when I sometimes get nervous that he'll leave me and go back to her because  we might have similar personalities because of our signs and it bothers me and makes me insecure and idk what to honestly ... He's proposing to me on Christmas this year but should I say yes ? Even though I'm having these thoughts?