I'm a little frightened that your boyfriend and his friend are clown freaks...
Clowns, imo, are a tad creepy. No matter how goofy or innocent they look.
To get over your phobia, maybe you could try a number of things. Things such as exposing yourself to a clowns slowly over time. Whether it be a photo, a toy, or even a full sized live clown. Just a little exposure every day might condition you to get used to them w/o fear. Like start out w/ a minute of looking at a picture. Then to being in the same room w/ it for 5, 10, 15, etc minutes all the way to an hour. Just slowly expose yourself to clown things.
It's key to take things step by step. So something like what I said above, but with physical distance. So maybe start small then work your way up to bigger clown things...
For example
1) Look at photos of clowns
2) Watch videos with clowns in it
3) Look at a clown person/item in person from a distance
4) Stand 10 feet away from the clown person/item
5) Stand 5 feet away from the clown person/item
6) Stand next to the clown person/item
7) Touch clown person/item
Try relaxation techniques as well. Being relaxed in fearful situations will help immensely.
I hope that helped.
X2. Exposure therapy. Just like they did on the animal planet show about people with extreme animal phobias. It really works.