Hi I would have to say and sorry to say this (I had to do the same) practice basic exercises till using the 7 string gets easier. If you know the "spider" exercise? This one helped me the most with every thing really. Try this.
Alt picking as you go up the strings( down actually but musically up). Starting on the low B, First finger, first fret 7th string (I had to think about it lol.) as you go up the strings pick first finger, 7th string 1st fret, then, middle finger, 6th string 2nd fret, ring finger 5th string 3rd fret, and pinky, 4th string 4th fret. Once you get to the pinky finger 4th string, 4th fret start back down. first finger 4th string first fret, middle finger 5th string 2nd fret, ring finger 6th string 3rd fret, pinky finger 7th string 4th fret. staying in first position next start the first finger 6th string 1st fret and work your way up the next 4 strings and back down again then start at the 5th string and so on one string at a time till you get to the D string. Then move down on the B string one half step and repeat the process all the way down the neck.
I'm assuming you don't know the spider if you do then just practice this and your basic exercises till it gets easier if not now you know. As soon as you get good at that try to reverse the order. Starting on the pinky finger 4th fret 7th string and work backwards from the original way I explained. I could not get used to it till I started to practice basic exercises. Also try to play songs that don't require the B string at all and try keeping it quite while you play. It took me around 5 month or so ( that I can remember) just to get comfortable. I still hit other strings while I play.
Hey I also had a Strandberg boden 7. Incredible guitar I had a trem bar. which I hated because if you deep dive with it the strings com off the saddles So I hope you didn't get a tremolo. I complained about it to Strandberg as well. They didn't care so I returned it lost 1000 dollars (because it is was 2300.00) and bought 2 Jackson v's and never looked back.
oh real quick I have a fiend that just got a 7 string Schechter and same thing "having trouble hitting strings, and getting used to it". I told him the same thing.
I hope this helps