I volunteer at an animal shelter, and this is a very common question. The relationship takes time to build, and you need to be patient and willing to follow the steps necessary to make it work. It sounds like you are ready for this and really want it to work. This is the first step needed. So, thank you for caring about your animals. Here are some steps to follow:
- Until both animals are comfortable, interactions must be supervised.
- If the dog is used to being crated, then crate him during your first few interactions. If not, use a baby gate and confine him to a portion of the house where he cannot reach the cat.
- Once the dog is confined, let the cat in the room to see the dog. Your kitty will be scared at first. That's OK and normal. Also, remember, hissing is not bad. It only means "I don't want any trouble."
- Let your cat approach the dog. Do not force any type of interaction. You will need to speak to your cat constantly, comforting and petting him (if he will let you).
- Have your cat's favorite treat ready. When the cat sees the dog, give your kitty a treat. After a couple sessions, he will start associating good things with seeing the dog.
- You can have your boyfriend do the same with the dog, if the dog starts to get jealous that the cat is getting food.
- The age and temperament of your cat will determine how many confined sessions you will need. Make sure the sessions are short at first and then gradually make them longer. You will start to see the cat coming into the room, cleaning himself, and probably ignoring the dog. This is actually a good sign. It means he's comfortable.
- Then, do the same steps with the dog behind a baby gate.
- Then, do the same steps with your boyfriend holding the dog on a leash.
Ideally, these steps should occur before the dog moves into the house, since this will take some time. If you rush the process, they may never be "friends." Also, as @Frisbee alluded, you will need a couple tall cat trees (at least 6 ft tall or taller), so your cat can get away from the dog when he wants.
If you follow these steps and let your cat lead the pace, you will have a happy home...and your kitty will be teasing the dog in no time. 😊