Jeanie! Our lovely lil' momma!
Although everyone is different, it'll take at least this long to start showing for your 1st pregnancy. Looooooooooooong ago when I was preggers with my 1st, I didn't show until I was 6 months along. Then, BOOM, I was out there! Like a basketball straight out front (it was a girl).
The tightness in your pants you are feeling is a good sign though! And as long as you are seeing the doc and taking your prenatal vitamins, you are good.