At 2 1/2 weeks, you don't even know you're pregnant yet. That's the first thing.
Secondly, if the woman's period is regular, she'll find out in short order by missing a period, and doing a test. If the woman has irregular cycles, she could go for a few MONTHS before thinking to test.
The tenderness and breast swelling doesn't really start to happen until around 2 1/2 months. Most women don't even show until the 4th month, and depending on her personal physiology, she may not show until well in to the pregnancy. I've known women who didn't start to show until the 6th month.
Pregnancy varies with each woman, depending upon her body type, inherited factors and a few other things besides.
Not all women get morning sickness in the first trimester. For example, I didn't have anything remotely resembling morning sickness until around 7 months. That was actually caused by eating too much at one time, with the stomach being squished by the baby. So I learned to eat much smaller portions, and more frequently (think hobbit with 7 or 8 meals a day).
Depending upon the individual woman's temperament, is also how she will emotionally handle being pregnant in the first place. I know I hated the last 5 months. But then again, I'm one of those women who don't understand how anyone could possibly be happy with having physical abilities limited because of this. Never did get that, the "I love being pregnant" deal.
Depending upon how large the child is in the last trimester, and how quickly it grows, also affects how you feel physically during that time frame. The last trimester is the period of the most growth for a fetus, particularly the last month.
And then you get to labor and delivery. Each pregnancy is different. For example, I was in labor with the first one for 18 hours, the second for 8, the third for 22, the 4th one for only four, and the last one for 14 hours. Again, depending upon the size and position of the child (barring no complications) one can have a variety of issues with the actual birth. First babies are honestly the toughest to deal with for the birth itself, as the woman has NO idea what she's getting in to. I don't care how many classes you go to beforehand, there is nothing like the actual experience to really teach you what is going to happen, and prepare you for future deliveries.
All five of mine were natural deliveries. Meaning no epidural, no spinal block, none of that. Just enough pain killer to try and take the edge off the pain of the labor itself. So then you have that to look at. Depending upon what kind of drugs one is given, whether or not the birth is c-section or natural, all play in to how much it actually hurts when the time comes.