I have been playing on E7-A7-B7 12 bars blues progression for a long time and I used Em blues Pentatonic Scale for soloing but which Pentatonic scale I must use when I am playing in Em-Am-Bm 12 bars blues progression?
You will be fine just using the E minor pentatonic scale. It contains the notes E, G, A, B, and D which are chord tones of the chords you are playing. It's not fancy, but it will get the job done.
When you have your scales down better you can star thinking of the progression more modally and use the chord shapes to influence your playing.
You are slightly confused. There are two pentatonics - major and minor. There are also two blues scales - major and minor! I guess you're using the pent. minor over the 7th chords. It's only a b5 missing from the minor blues. They both work fine (if you're careful or lucky!) over the 7th chords, and will also work fine over the minor chords. You will soon find also that the major pent and major blues will work over the 7th chords, BUT NOT over the minor chords.
For an Em I-IV-V I asked a similar question and have been doing quite a bit of experimenting with this. What I have found that works best for me is to play the minor pentatonic of the I chord, or the key that the progression is in, then sometimes (not always), switch to the pentatonic minor of the IV chord or chord. But that's if you are comfortable doing it.
OR, and this is even better and more flavorful is to play the Dorian of the IV chord in the progression. So, play the G major scale but center from the A note, get to the 1-3-5-7's regularly and the rest is flavor - pull-offs, bends, hammer-ons, or just play. It sounds pretty good.
For I-IV-V 7 Progression Play the major pentatonic scale or play Lydian or Mixolydian of the IV chord. Experiment!!