Right now my followers are serana and frea but i can seem to get rid of frea..... and also i have problem with getting other companion even though i have UFO (unlimited followers overhaul)

UFO hasn't been updated for DB and thus avoid using DB followers at all costs.

Use console command set playerfollowercount to 0 to get rid of her - at least that's what worked for me.

UFO should have a hearthfire and Dawnguard patch though.