P.M.
If having your child in your bed because the child sleeps and feels better lying with Mommy is hard on your marriage - looks like your oldest child, I mean husband, needs to grow up.
There are MANY places besides the bed to be sexually intimate with your spouse. There are also date nights, hotel rooms, sofas, dining room tables, backyard, etc...
Your spouse should not come first. You are a Mother. You are considering to force wean your obviously needing to nurse son because you think it will get him in his own bed so your husband can have sex with you whenever he feels like it?
1) Bed-sharing is normal and infants and toddlers are designed to want to be with Mommy for nursing and sleeping to feel safe, comforted and loved. It's how they develop.
2) Nursing a toddler is also normal - in 98% of the world... but not necessarily in America. Good for you for stepping up and doing what your child needs.
3) Tell your husband to grow up, your children will not need or want Mommy (or Daddy) all their lives and will grow apart from you sooner than you are ready for. Enjoy this sweet, loving innocent time while you can.
4) As a last resort, try bringing the crib in your bedroom, take off one side and attach it to your side of the bed. Co-sleeping is the next best thing if bed-sharing needs to end.
I bed-shared with my daughter since she was brought home from the hospital. We've had a lot of ups and downs... but I do not regret a day of it. I was dating a man for 2.5 years and told him my child came first and if he didn't like her sleeping with me, he could get his own bed or use the couch. We are now married 3 months, my now 5 y/o still sleeps with US, and she is finally ready for her own room and bed. She's very happy about being ready for the next step and we've been very happy and supportive with her. She's made up her own mind, she's ready to be a big girl and have her privacy. it's a BIG thing!!