I’m wondering how to deal with attachment issues from childhood and adult romantic relationships?

Your first step is identifying just what you have stated, that perhaps your reaction that you have in your body does not match the event that is happening. That is a huge 1st step! You can work on managing your physical responses by using several different types of techniques. Passive bi-lateral stimulization can be helpful in the immediate time frame to get control of your physical responses. Just as you see moms with babies start to walk the babies when they are upset, or to sway rythmically to calm children, you can also utilize physical movement to calm your body. This may give you a chance to think things through without the intense physical response.

Another option to get "out of your body" is to actually focus on immediate things therefore changing the impact of those past issues.

Consider noticing the changes in your body; close your eyes and say 5 things you can feel with your body, 5 things you can hear, 5 things you can touch, 5 things you can smell. If you cannot find 5 find as many as possible. This helps your brain focus on the "here and now" of your experience instead of the past that may be triggering your physical experience. This is just another way to ground yourself in the present and help your brain understand that you are not in the same kind of danger, physical or emotional, that was in your past. Your brain can re-train to recover from pain, much like we condition our bodies with exercise. 

These and other techniques are easily teachable. You also show insight into things that have happened to you in the past that may have been traumatic and looking at those and understanding how they are manifesting in your current relationships is a great idea. I would be more than happy to help you work through some of those past dissappointments and separation issues. You seem to know yourself pretty well and have good insight into what is happening. The task now is to understand it, change how those memories are stored so that they don't continually crop up and inhibit your ability to go forward in your current relationships. Change is completely possible and you appear to have the insight and first step to change in the palm of your hand already. 

StarrLee Heady