Can I be intimate with my husband during my first trimester of pregnancy?

Yes. Sex is considered safe during pregnancy as long as the pregnancy has been progressing normally. If there have been problems with your pregnancy the best thing to do is speak with your obstetrician. Sex during pregnancy, even in the first trimester, will not cause miscarriage and should not be a reason for concern in the absence of other problems.
Sex in pregnancy. Yes, unless you are having bleeding, or history of recurrent miscarriage and cervical incompetence. Otherwise there is almost no risk to the pregnancy.