Merging can be a very difficult process, and can often make little problems in the relationship really big problems. My partner and I have been living together for 2 years. At first I put all of my things into storage, as she had a completely furnished house and the only things I brought with me were personal belongings and my childrens things. But paying for storage seemed silly, so eventually i sold or gave away most of the stuff I had.
There are occasional spats about things being "hers" or not mine, and the fact that if something were to happen and things didn't work out for us, I would be starting over from scratch. But to me things are just things, my family is more important than any thing I could buy.
The most difficult challenge for us has been the merging of our family. I have 2 boys ages 5 and 3, who are autistic and deaf. She has a 12 yr old boy, who is adhd. Needless to say we have our hands full lol. We were both raised very differently and have very different parenting styles. It makes it very difficult to raise our kids together, but we compromise and try to stay united on issues that may arise, and remind ourselves that at the end of the day we have learned a lot from each other, and grown as individuals as well as a family!
This is a good topic, I am sorry that the merging process has been so difficult for you. Not knowing many details it is hard to offer any advice, but communication is always a great place to start!