Can I pump while pregnant?

I’m almost 21 weeks pregnant with my last baby. I never breastfed my first but my milk didn’t dry up until I got pregnant with my 2nd and was close to 20 weeks but it wasn’t a lot. My 2nd was born at 25 weeks and I pumped while she was in the nicu but she had to leave on formula because my supply ended up dropping. She is 10 months old and I’m in so much pain from making milk. Would it be safe to get a manual pump just to relieve pressure when it gets painful or should I just hold off? (My doctor is no help because every appointment I have to see him ends up with me just seeing nurses that don’t give me an answer)