My last period was Dec. 8, 2013... its been 37 days I still don't have my period... I have a regular cycle ay 26-31 days... Been on medication, 2 sets of antibiotic from Dec. 26-Jan 1... My husband and I did a contact on January 4... Could I be pregnant?

Did a "contact" do you mean had sex ? I will assume, and you and husband only had sex one time all month ? That is another issue

But the antibiotics, stress, health issues can all cause delayed or even missed periods. And sometimes they are late, or even missed and no reason is ever known.

Since you (I assume) had sex, then of course you could be pregnant.

It is too early to test, you need to be "at least" 2 week late and even then false negative are possible.

So wait about a week and do a home pregnancy test, with first urine of the mornign as soon as you wake up

As well antibiotics can mess around with hormonal birth control and cause a unexpected ovulation. But as the Friar said, you need to wait until two weeks after when you expected to get your period; worst case of course. So another week or so. Then take the home pregnancy test.