I remember when I started doing longer road rides as a teenager, by the time I had done 90km in a day I always thought my rear tire was going flat or my brakes were dragging. To this day I get on my generally perfectly functioning bike and I stop to check for brake/tire/bearing problems just because I am having a bad day.

My probable diagnosis: It's not the bike. The OP is a stronger rider now than he was months ago.

To the OP: Run your tires at whatever pressure you feel most comfortable, but running the pressure too low (especially on narrow tires) will almost certainly lead to punctures.