Does Mood Swings, Pink Vaginal Spotting And Nausea Indicate Pregnancy?

I had unprotected sex 18 days ago and today I began feeling out of the ordinary symptoms. Throughout the day I've had light spotting - the color was extremely light pink. By mid morning I began to feel very tired and weak and I did get enough sleep the previous night. By this evening I began to feel nauseous and am still tired. The other biggest issue I've been having this afternoon/evening are sever mood swings. I am taking ortho tri cyclen, but missed two days in a row and do not consistently take them on time each day. Since I had the unprotected sex 18 days ago, I have had unprotected sex several times since then and my husband has ejaculated inside of me. Could these be early pregnancy symptoms I am noticing?