I had brown discharge with red spotting . one day before my period . would i get pregnant if had sex one day before my period start?

No: It is very very unlikely to get pregnant the day before one's period starts, if the period actually started the next day. If one did turn out to be pregnant, then either she was already pregnant from the prior month, or her "period" was not her true, regular period.

Possible: If truly one day prior to menses, then unlikely to get pregnant. However, it is not unusual even for one with regular menstrual cycles to occasionally have an irregular cycle such as ovulating later in their cycle, making conceiving a day before "expected menses" a possibility. Thus, if trying to avoid pregnancy, would be prudent to use contraception such hormonal contraception and/or condoms.