Thank you for writing to JustAnswer with your question.
In most cases of deep vein thrombus, there would be some swelling or edema in the leg, redness or inflammation along the vein area (often felt in the back of the knee).
But, sometimes these symptoms don't show up, especially in a young person who may have excellent collateral circulation.
Sitting in one position for a long period can predispose one to this problem, especially if one is also dehydrated - has not been drinking much fluids. This is one reason why DVT may occur to an individual who has been on a long car ride or airplane ride. In fact DVT from this cause is sometimes called "business class syndrome" because the cramped seating in an airplane may predispose an individual to DVT.
Although you sound like you have researched the topic already, this is a good link for future reference:
Due to the amount of pain you have, and the fact that treatment is better to start sooner rather than latter, you should go to your doctor (probably too late in the day) or an Urgent Care Clinic or ER today. They can do some simple blood work and an ultrasound of your leg to check for DVT.
I hope for your sake this is a sore muscle from starting out an exercise plan with a 3 mile walk, but we cannot take the chance that it might not be. I do hope you continue to exercise, drink plenty of water, and get up from your desk every 2 hours at least from now on, no matter what the results.
Hello and thank you for clicking on "accept"t and for the nice feed back you gave me. In the future if have a question that you would like only an MD to answer, place it in the JustAnswer "Medical" category. Nurses (mostly advanced practice or educated beyond simply an RN) and other health care providers such as Pharmacists as well as the MDs can answer questions in the "Health" category. But, the "Medical" category questions are answered by MD's only. The differentiation of categories is a recent change. There are also some new specialty categories such as Opthamology, Womens Health, Pediatrics, Urology, and Dermatology (no orthopedics or sports med. yet) available now that are only answered by MD's. Questions may go unanswered longer, especially if they are priced low. JustAnswer is still recruiting physicians for these new categories.. But, saying that, most experts in the Health category will not answer anything that they are not capable of answering. And for example with me, I have over 25 years of experience(including ER -where nurses often do the first assessment and get the ball rolling before the doc can get there) and a MSN, so I have a wide knowledge base. But, of course, the depth of my knowledge is limited in some areas.
I realize that this is more info. than you likely expected or wanted, but there is a lot of mis-information and confusion about what a nurse does (plus there are so many different educational levels possible) so I like to do my bit of public education when the circumstance warrants it. Nurses are still most often misrepresented in the media, including on House or Greys Anatomy, most often the doctors are shown doing many things that in actuality an RN would be doing. And there just aren't that many doctors in one hospital! (In a teaching hospital the ratio of doctor's is higher, but still not near as high as shown on TV!)