Meditation is a struggle
I usually feel heavy and drowsy.


This is Slot and Toper. You should overcome this and other Hindrances. Many of the techniques are found in: 


The Five Mental Hindrances and Their Conquest Selected Texts from the Pali Canon and the Commentaries compiled and translated by Nyanaponika Thera
Nīvaraṇa by Piya Tan
Thīna,middha by Piya Tan [these might also be interesting: Vyāpāda, Uddhacca,kukkucca, Vicikicchā, Kāma-c,chanda by the same author]



  ...  Feeling intense Dukkha today.


When you do not achieve spiritual goals unsatisfactoriness may arise. [Sal,āyatana Vibhanga Sutta] Best is try to keep you mind and practice steady. Also see if you are putting too much effect leading to restless worry. Also do not measure progress too often. Just do what needs to be done, i.e., just practice!