Letro will work very well to lower estrogen. Its the strongest AI for the job. Problem is, you don't want to lower your estrogen too far. Low libido would be one side effect of low E. What you will want to do is reduce your letro dose. You're taking too much. AAS is all about balance. I would reduce your letro and over time, your sex drive will return to nromal. It may take a couple of weeks. So if you are taking 2.5mg letro, reduce it to 1.25mg and see how you feel in a week. If it is still not better and you are not having any gyno issues, try to reduce the letro a little further. If you want to get the most clear pictiure possible, of what is going on, get some lab work done. This way, you don't have to guess. You can know exactly what your estrogen level is and it will better inform you as to what you want to do with your AI. 

As for HCG, you'll want to do some more reading on this one. Just so you understand it a little better, heres how it comes into play for BB pruposes. When we take gear, it shuts off our natural test production. In a nutshell, HCG will force that production back on, kind of like a primer to get your engine to turn over. It will help the engine turn over. So theres no such thing as cleaning any kind of receptors.