Well im not sure how to go about it boyfriend help?

well me and my bf have been together for 3 years and we have been through alot and it took us 2year aa half for us to live together and im ready to gt married im ready to start our family he is frm mexico and he is planin on goin back this december which i dont mind bt he wants to prepose to me with a ring before he leaves and then me wait for him.. he wnts to knw if he can trust me while he is gone like i said we have been through alot i cheated and he has too and i think dats whats keeping him bt i have gt his trust back bt im nt sure if its all of his trust i mean i do trust him now bst im tired of waitin i wnt to marry da guy