You know, it really is okay to keep breastfeeding as long as you both want to, including in public. DS is 4 months old, and I will be for some time to come.
When I start BLW at 6 months, I'll introduce water in a cup. We might sometimes try ebm in a cup too, though probably after he's got the hang of it (less spillage). I've played at expressing, but have frozen my attempts, so wolfcub hasn't had anything but straight from the source so far. I think we'll skip bottles.
Its up to you what you do, but try not to feel self concious about bfing in front of other mums who are bottle feeding. Seeing you bf in public might make them feel they can too, if not with this baby, then maybe with the next one. Some mums use ebm in bottles when they are out, others use cartons but they may still be breastfeeding at home.
If you try expressing, then it can be more successful to get a good letdown if you are feeding your baby off the other side, or if she's close by. If not ten try having a picture of her/imagine its her feeding not the pump. Don't be disheartened if you don't get much the first attempt, just try again at roughly the same time the next day.
Just because ebf is recommended till 6 months, doesn't mean you have to stop or hide away after then. If you want to stop, that's totally up to you, but don't expect to get your body/life/sanity back just because you stop bfing, that's more to do with becoming a mum! Breastfeeding once solids are established is usually less intense because the sense of responsibility of being the sole source of food and drink lessens, and they can have a solid meal with water when you aren't around, extending the time you can have away.
Their looks may be more about how they feel about their own choices, or trying to offer you privacy rather than being judgemental.