Estrogen agonists like Nolvadex WILL NOT reduce estrogen, will not likely reduce bloat very much, and will only be good for some people to prevent the ONSET of gynecomastia. In fact, in those that are very estrogen sensitive, a drug like Nolvadex may actually worsen estrogen-related sides.
HCG will RAISE testosterone levels, even if you're already taking testosterone, which if you're already converting testosterone to estrogen from high doses of testosterone, HCG will just give you that much more testosterone for your body's enzymes to convert. Why? Because HCG acts like one of the chemicals your body produces to MAKE testosterone! HCG is good to use during cycle ONLY for the purposes of testicular size and weight or as an additional component of your TRT if you're keeping your testosterone dosage low.
It makes sense while supplementing with testosterone to use an aromatase inhibitor to combat estrogen-related sides. The three major ones are anastrazole, letrozole, and exemestane. Keep in mind that non-steroidal AI's generally wreak havoc upon your lipid profile so if you have access to exemestane (Aromasin), then that's your best bet. In any case, regular bloodwork in the above areas is a responsible pursuit.
People certainly use Nolvadex while on testosterone but I would save the Nolvadex (tamoxifen) for post cycle recovery of your LH and FSH levels so you can start producing testosterone on your own again. It works well for that purpose.
Research is key here to know exactly what dosages should or should not be used and remember to keep in contact with a doctor that specializes in one way or another, hormone replacement or especially testosterone replacement therapy.