Chances are you would get away with it, but I would strongly recommend you don't do it. Some people like myself are very sensitive to the damage MDMA can cause and it would be impossible to know this until its too late. Also, you really do get a limited number of 'magical' MDMA experiences, and every time you take it without at least a 3 month break you are reducing this number. By using sparingly at sensible doses right from the start, you should be able to enjoy using the substance just as much as your first time for much much longer.
As for what the actual risks are, well, some people will disagree with this because its never been 'proved' (mainly because the research hasn't been done), but I think it's hard to deny that MDMA is in some way neurotoxic, and it can instantiate changes in cognition, anxiety levels and mood that can last a very very long time before full recovery. At first this is not noticeable, maybe a bit of midweek blues and a foggy feeling of dumb content-ness in the weeks following. I think the issue is that even when you feel seemingly fine again, everything might not be exactly back to normal quite yet neurologically, and taking it again in this period has a compounding effect, so you can very quickly end up in the situation where the negatives have become very intense, the drug has almost completely lost it's 'magic' (but you still chase it), and the negatives you feel at this point take much much longer to go away... years, for some.