My doctor gave me through rubella vaccine and chicken pox vaccine at the same time. I read on some fact sheet that it shouldn't be. Is this ok?

Sure, no problem! Most vaccines can be given together. For example, the routine kindergarten shots are: measles/mumps/rubella, chickenpox, polio, diphtheria/tetanus/whoopingcough . . . Which equals 4 injections (2 in each arm) at the same office visit.
It is ok. You can give it on the same day but administer it on two separate limbs.
Yes. These can/should be given on the same day to avoid an unnecessary extra visit. If not done on the same day they should be at least a month apart.