Plan b - missed Third period? when do symptoms start?

Hi,

My Girlfriend and I had unprotected sex around the date of April 6th. We were worried about it so she had taken plan B on the 7th.

About 4-5 days later she had a period, and we assumed it had to do with the dosage of hormones that the plan B gave her.

Her normal cycle used to have her get periods around the last week of every month, from the 23-30th roughly(closer to the beginning)

After that hormonal period, she did not have a period for awhile until the beginning first week of May. I assume that her regular cycle got pushed back a bit.

It is now roughly a month after her last period, and she has not gotten anything yet. She is worried because it has been more than a week since her typical period would've started around the 23rd.

We have had unprotected sex a couple of times in the last month(please don't judge us) and never have I ejaculated inside of her.

I was wondering if her cycle could be completely changed now, and we should wait another week to see if it comes OR if she's pregnant.

A few days ago, and also this morning she said that she briefly felt that it was coming and she was cramping, but nothing so far.
D
At what Stage of pregnancy does morning sickness and other symptoms arise? She has not been complaining of anything that I know of, just no period.
Any input would be greatly appreciated. Thank you!