Is this implantation cramping?

My DH and I have been trying for 21 months to get pregnant with regular checks to make sure we are both healthy. We have been charting BBT and using OPKs. I got my positive OPK on cycle day 13 and we were BDing every night starting 5 days before until 4 days after Ovulation. At 5 DPO i had some lightly brown spotting. I am now 8 DPO and having very bad cramps and a tight feeling in my lower abdomen. I am also very tired, napping during the day with my son, and the sight of raw meat is making me nauseous. I was just wondering if anyone has ever had these symptoms and ended up getting pregnant. I am so tired of getting BFNs and I really feel this is our month. Thanks in advance for any help you can give.