I do not get turned off. I actually prefer smaller breasts, to be honest, so I may not be the right person to answer this question, but saggy breasts aren't a turn-off at all.
Should you consider a reduction? Well, that's a complicated question. I wouldn't consider it just because you are a little insecure, although that's just my opinion and many women choose to have cosmetic surgery on their breasts. Certainly a reduction is more natural than enlargement, but you should talk to a surgeon about this if you're actually serious and look very closely at the risks and costs. But if I were you, I'd be happy with what I have. Most guys love large boobs, so don't feel too self-conscious about it.
A more important factor, to me, is whether it will give you back pain. Certainly having too much weight there can cause problems later in life. That's another thing you should take up with a doctor, though.