#1
I’ve recently started playing with a pick and I’ve found that after playing for a few minutes I begin to experience an “ache” in my upper arm, do I just need to get used to playing with a pick or am I doing something horribly wrong?

Cheers.
Gear:

Fender Jaguar Bass
Ashdown MAG300H Head
Ashdown 410 T Deep Cab
Epiphone Thunderbird
Squier P/J Bass
SKAK20BA Practice Bass Amp
#2
I think its probably the angle you holding your arm at. Is it higher then normal. Maybe you could mess about with different strap hights And see if that helps.
Yamaha TRB1006
Fender MIA jazz bass
Hora Hybrid double bass
Hartke lh 500
Ev 606L
Epiphone les paul
#3
fatgoogle is probably right but when i had the same problem i just laid off the bass and played the guitar for a week or so and it hasnt bothered me since.