If you were still married to another man when you married this man, then your marriage is not valid. If your prior marriage is now dissolved, you should contact the local or state office that handles the registration of marriage certificates and find out from them how to remedy this situation.
Sometimes it amazes me the foolishness of people. If you are married, why on Earth would you go through with the second marriage before the first one is terminated? Did you tell the person who married you that you were already married? Probably not as the person wouldn't have married you. And no one knowing this spoke up? Sad state of affairs.
AS to the answer, yes you are legally married. The reasoning is that at the time that you were married to the second husband, the marriage was void (meaning not valid). After the divorce to the first husband was finalized, then the marriage changes from being void to being voidable (voidable meaning that the second husband had a chance to declare the marriage void and walk away) so long as your second husband knew all of the facts. If he doesn't walk away within a certain period of time, then the marriage is considered perfected (valid) as despite knowing of the flaw, he choose to remain in the marriage.
To put it in other terms, say the law says you can only own one dog. You put the first one in the paper for sale but due to a new litter of puppies decide to get a second dog before the first one is sold. At any time while you own the two dogs, there is a violation of law which allows the the second dog to run away free and clear or the dogcatcher (law enforcement) has a right to charge you with the crime (bigamy). Once you have sold the first dog, then the second dog has a limited time to leave or you are considered the owner and are now liable to keep the dog; the license for the dog is now valid.
So if you are asking because you want to make sure you are legally married - you are.
If you are asking because one of you want out of this new marriage, it is likely you need a second divorce. If you are seeking the have the marriage voided or divorced, you need to consult with an attorney to look at the exact dates for the timeframe to be analyzed for the factors to be properly placed to determine what action needs to be conducted to invalidate the second marriage license.