Nope rest assured that you are not a jammer, from what you say you are being unilaterally awkward and deserve every bit of the pounding you are getting and in my personal opinion you should probably get a good deal more.
You take the gloves off by putting some resistance without cheeking with your partner may be he trying to work on his movement or flow and the last thing he needs a numb-nuts resisting.
I am all for resistance training but there is a place and a time and it need to be bilateral and agreed upon from the onset.
You would laugh if I said that I am going full on all the time because I want to give my partner a good ukemi practice and if I was wondering why people call me a beast.
Well resisting without telling is exactly the same.
Based on what you wrote, when is it a good time to begin the practice of aiki in Aiki-do? I cherish every moment I spent on the mats and I trust my training partners but the trust is broken once they decide to hurt me after I have given in to their waza.
You will probably laugh your head off if you realise that the peers who branded me a jammer are a head taller than me and 25 or more kilo heavier than me and can out muscle me anytime they want to. One or two will not hesitate to put their 80-90 kilo bodyweight on my elbow in a nikkyu lock with less than 6 inches of space between the face and the mat. They will not hesitate to remove your hand from the wrist in sankyu. For shihonage or iriminage, if you are lucky, their follow through can be just 3 inches about the mat, if not, it is 3 inches below the mat. All these, they won't be telling you and so much for good ukeme practice. If you are beast, then I don't know what to call them. At the moment, they are just Pain, Painer and Painest. BTW, Painer and Painest are the Yoshinkan guys disguised as aikikai beginners.
Hope to see you on the mats.