Pregnant!!! But just have a couple of concerning questions please hlp?

I went to the doctors on Monday for a blood test for pregnancy i have been having all of the symptoms when i took the test it came back negative and my HCG levels were at 2 they told me to come back in 48 hours so I went on wednesday and they took more blood and they told me that the blood test was positive and my HCG level was at 28 so I am wondering what this means a 28 hcg level I have also taken 3 HPT and all came out positive so I know I am pregnant. My other question is, is it normal to have nausea every single day and then not get it as much or at all the next 2 days?