Welcome to HCM
We understand your concerns
I went through your description and I suggest you not to worry much. The testicle and its sack are virtually not connected to each other. Testicles are almost free to move and we can notice this early morning and night when the sack is loose enough. Also during the sex, sack loosens a bit to allow the production of sperm and during that time the testicle is again free to move fore and aft. The description you gave is normal and there is nothing to worry about it. Stop worrying about it and concentrate on your studies.
You might need psychological counseling
., I am more than happy to provide telephone psychological counseling through healthcaremagic. Contact me through customer care, www.healthcaremagic.com.
Hope this answers your query. Available for further clarifications.