I had an ex who's already huge boobs used to go up almost a cup size sometimes with her period, which was awesome. Anyway, we went on a trip once and she must have had this pre-planned because her period came and she whipped out this push up bra i'd never seen, and wore a low cut dress showing about a metre of cleavage and teased me for a full day of sightseeing. Every change she got she'd tell me that she was going to titfuck my brains out when we got back to the hotel that night.
Finally back at the hotel I ripped that dress on, dumped some lube into her cleavage and went in while the bra was still on. Had only been in for a second or two and I came while she was rearranging her bra and shifting my cock into position