I had an ultrasound and they didnt see a baby but the urine test is postive and my hcg level is 75.... how early can i be? period twice this month

Hard to tell: HCG levels vary widely in normal pregnancies and are not a good indicator of the time since pregnancy. If ultrasound was negative, you are very early in the pregnancy. You may wish to see your doctor in a few weeks and s/he may be able to provide an estimate on repeat ultrasound.

Too early: ultrasound will not be of value in dating a pregnancy for about 2-3 weeks. At about 4 weeks an ultrasound will begin to see signs of pregnancy. Patience will be of value.