Is it possible my daughter is being abused?

Sorry in advance I didn't know where to put this at. I have a 21 month old daughter. I worry she may be being abused in one way or another. I'll try to give all details of why and the whole story.
All of these signs and intuition started when I started CNA classes back in January 2015. I needed an extra babysitter and her grandfather offered to watch her since her grandmother works on Wednesday and Thursday's till about 2.  Well I didn't think anything of that till now or him constantly wanting to see her now and all of a sudden having this deep love for her that wasn't as deep before. I used to just chalk it up to oh she's older now so she's fun and can play around and talk a bit so that's why but it struck me off recently because I remembered how when I used to try to get him to watch her for me when she was younger such as an infant till about the time she was 15 months he didn't want to watch her he'd actually just tell me flat out no because it wasn't something he ever did before. Well while I was in school a couple of weeks later probably almost February my daughter randomly one day WOULD NOT let me wipe her vagina. She would tighten her legs so tight I couldn't even get them apart and she hit and kick and scream when I tried to clean her there. She didnt care if I wiped her butt but when it came to her vagina she fought me like I was gonna hurt her always with this look of please stop. She also had a lot of diaper rashes during that time of the three months I was in school. I began to notice she would cry really hard and cling to me if she was being dropped off with just her grandpa home. If grandma was home with him she would happily get down and play and run on with the occasional sadness that I was leaving. I called my fiancée crying saying how I feel like she is being abused and he tried to reassure me that she just misses me just like his mother(the grandmother I'm talking about) said when I would mention it to her. No one listened and I was told I was just imagining it. Well my daughter ended up coming home one day with a bruise on her spine maybe the size of a penny or a nickel and it was in the middle of her back. I thought it was a bit weird that she had a bruise there and tried questioning everyone but it seems no one had answers. On top of all of this her grandfather will allow her in the bathroom with him while he is peeing and doesn't even try to prevent it even when we are there. He used to prevent it back when she was younger and walked in on him he would close the door on her and say no no honey you don't come in here but now all of sudden he doesn't care and even doesn't try to close the door when he knows she'll follow him. I'm just worried that it is happening and I am beyond terrified because I was abused as a child and I really don't want that to happen to my child! Me and my fiancée don't know what to do because we don't know how to address this or go about figuring it out. I'm just utterly concerned especially when I'm going back to work again soon and if I'm working days he would get her two days all day. Any advice is helpful! Thank you all!