I am not religious either, and that is because i hate rule keeping, yet I also believe I am a deeply spiritual being
I guess you are not alone in your fears, but marriage is kind of like a non factor in afterlife.
Many Christians confuse "heaven" with a largely Greco Roman view of afterlife - Where people sail up to heaven after they get their wings... Float around from cloud to cloud.
The Bible actually teaches that God's home is in the heavens - that God lives very far away and yet is also very present all at the same time, so God is holy and that man is seperatd from God and his purity and glory because of sin and cannot be with God as God is immortal and people are mortal.
The New Testament's view of afterlife is one of physical Resurrection -> As you know It was said that Jesus "resurrected" on the third day and the Greeks had trouble with this kind of thinking because the body was a curse in the first place -> the body could not go to the heavens and why would Jesus want to resurrect in the first place, incidently many Christians believe Jesus visited hades or hell (buried for three days) before his resurrection before ascending to the heavens just like greco-roman gods (Jesus resurrection was bodily and his ascension was again physical) THis idea was troubling to the Greeks.
I will refer you to the NT book of Hebrews 13 which explains clearly that "all the saints" await a bodily resurrection a glorification where those in Christ Jesus get a new body and the curse of sin is forever broken.
2 Corinthians 15 explains how the dead body is like a seed not really dead at all but comes up from the ground a new body, how the glorified bodies will differ from each other as each star in the expanse differs in glory, the story here is that God on't be mocked -> you don't plant a walnut and get a celery stock, God will rememeber each seed that went in the ground and give a body as he deems fit.
Marriage, pro-creation, sex are not really expanded on in the afterlife, and I guess we'll see how it all shapes up -> but I personally do not accept this Greco-Roman view of Heaven and hell, I don't believe in a hot hell with burning flames and triton jabbing at your side, I also don't believe that a loving God creates a second room next to Heaven where people are punished eternally for their sins, I do believe however that if you don't want to be resurrected with God that God will honour that and simply annilate anyone who does not want to be with him.
The New Testament Bible teaches about "resurrection" the Greeks viewed the soul as eternal and many if not most Christians I meet view the soul as eternal yet the soul was created by God and if a person does not wish to be with God eternally
I think it is a leap to say that just because we receive a physical body at the resurrection of the dead we will have intercourse with out former wives, glorification suggests perfection even as Christ was perfect and we just don't know it looks on the other side because the ENTIRE church awaits it's RESURRECTION.
I know this raises other questions like what does God do with the "dead" while they await their glorified bodies at the resurrection, but I think unless you ask I will time out for now...