Am I pregnant or maybe just false positive.

So not going to go to into detail. Me and my SO did the deed twice in on day. Didn't wear a condom so he just finished on me but I started thinking about pre-ejaculation. Need I mention I was ovulating and I am not on any BC. I have heard about some people being pregnant and not knowing but I wanted to ask real people instead of just searching up everything. I feel like I am around 2 and a half months pregnant. I have had a period the past two months they were short and light. Now my period is suppose to start but is no where in sight. And the past few weeks I have had back ache, headaches, nauseous, peeing frequently, bloating, and fatigue. Which some of these could be easily explained but the main on is my missing period and I know most people would have known by now but some people don't know till after three months. I love kids and I would be happy if I really am. I took four pregnancy test and one out of four said positive. Which makes me doubt but I have also heard that some people with a low amount of a certain hormone they won't get a positive.