Oh don't worry too much, swollen, darker areolas and that numbness you're feeling are really common in the second trimester, because your body is already preparing for breastfeeding and hormones are doing a lot of work around that area. The whitish spots on your nipple are most likely Montgomery glands (little glands on the areola), which become more visible during pregnancy and are completely normal, they actually help keep the area moisturised. Someone in my mum group mentioned that the numbness and tenderness tend to ease off as you get further along, though a few mums said it came and went throughout the whole pregnancy. That said, since you're noticing it specifically when you press on it and it feels better with pressure, it's still worth mentioning to your gynae or midwife at your next visit just to rule out anything else and get that peace of mind.