I assume from your question that you received a 20 day sentence for the dws charge, and you are awaiting a violation of probation hearing from probation stemming from the underlying 2nd offense dwi charge. My first question is how much backup time do you have from the second dwi offense? The court cannot sentence you to any additional jail time unless you were sentenced to a period of incarceration that was suspended. So, if you received a one year sentence, with all but 10 days suspended, in the 2nd dwi case, theoretically the court could impose the entire 355 day balance of the suspended time. When you say you were "convicted" of dws, did you have a trial where you were found guilty, or did you enter a plea? The problem with a violation of probation hearing is that it is generally considered to be civil in nature, and the State only needs to show that you violated some term of your probation by a preponderance of the evidence, not beyond a reasonable doubt. This is a much lighter burden on the State. Finally, what provision of your probation does the State allege you violated? Obey all laws? The likelihood of the State prevailing in a violation hearing depends on the condition alleged to be violated, and the method by which your dws case was handled.
It is possible that you can take immediate steps to mitigate damages in your violation of probation case by immediately entering and completing a residential alcohol treatment program. Courts often give day-to-day credit for time spent in in-patient treatment towards an active jail sentence, so depending on the county in which you are alleged to be in violation of probation, and the particular judge, in-patient treatment may keep you from serving any additional active time. I strongly encourage you to consult with an attorney in the county where you were charged. Most criminal defense lawyers are familiar with the judges in their county, and can give you a more precise prediction about the likely outcome of your case, and the likelihood of avoiding active time by completing an in-patient program.
There are many issues raised by your question that you may need to explore with a good defense attorney. Were you represented by competent counsel when you entered the plea in the dws case? Were you aware that a conviction would violate your probation in the dwi case? Is it too late to file a motion requesting a new trial in the dws? Was a motion to reconsider sentencing filed in either case? The answers to these questions will likely impact the advice you receive, so be careful with any lawyer that doesn't get a thorough background from you. Good luck!
This advice does not/is not intended to establish an attorney-client relationship. This advice is general in nature, and is naturally limited in scope and applicability to the limited factual scenario presented in your question. This advice should not be relied upon by you and you should take no action as a result of this advice unless and until you have met with the advising attorney and apprised her of all pertinent facts associated with your inquiry. You should immediately consult with a licensed attorney for advice specific to your case. Moreover, as reasonable minds often disagree, you may find that advice rendered to you based upon your circumstances may vary based upon the opinion(s)/experience and other intangible factor(s) comprising the experience and knowlege of the advising attorney. You are, therefore, encouraged to seek another opinion. Reliance on the advice given in this answer is entirely at your own risk, and you specifically agree that there shall be no liability whatsoever or redress for you, of any sort, for any damages or other cause(s) of action against the advising attorney.
You need to contact an experienced criminal lawyer asap. It could be that you are facing the 10 days that you got for the DUI plus whatever sanctions are imposed for the DWS. This is not something that you can handle on your own. Get a consultation from an attorney in Ocean City.