Twin pregnancy

Hello, good pm. 6weeks+ preggy with 2 sac seen on utz, may nakikitang part na din ng embryo but wala pa heartbeat kasi too early pa daw. Sa mga twim mom/preggy jan, normal lang po ba yung almost everyday masakit likod-balakang at puson? (pain lang oa na dysmenorrhea) And nka ranas pa ng LBM and OA na skin allergy po? TIA