Is It Ok to Do a BBL if I Previously Have Had Minimal Lipo on Stomach?

Yes, you can still have a BBL even if you have had liposuction in the past.  In fact, many of my Brazilian Butt Lift patients have had previous liposuction.  BUT, it is unlikely that further liposuction on your abdomen will smooth it out, in fact, it could make the lumpiness more apparent.  Liposuction can lead to formation of fibrous tissue - almost like a scar underneath the skin.  This can lead to an uneven appearance.  More liposuction in the same area might cause more fibrous tissue to form.

Based on your story yes you are a candidate for liposuction, fat transfer to buttocks, and sculpting the buttock, the Brazilian Buttock Lift (BBL)

where every you have diet resistant fat: 1) abdomen, 2) flanks, 3) inner and outer thighs, 4)back, 5) knees and 6) arms this fat can be purified and injected into the buttock.

this technique involves more than just the above but an  artistic placement of the fat to get the shape of the buttock you desire

Make a  appointment with a experienced, reputable board certified plastic surgeon.