Dating Forum - Sad And Confused And I Just I Dunno Where Else to Go

Hey there this is my first post her and I really need some help. I met this girl online and we have been hanging out for about a month and it was really starting to go somewhere and we were together on valentines day and stuff and it felt really great. But she tends to really re think things alot and v-day she said she wasnt so sure about us anymore.Ive really felt like crap the last 2 days and ive been tryna talk to her and stuff but it seems like my confidence is gone. She really scared me saying she wasnt sure she wanted to be with me. Now things seem to be getting back to normal but ive been still been really depressed and the only thing we can seem to talk about anymore is depressing relationship stuff and I dont know what to do anymore. Please help.

I also should mention...
Im 20 years old and am a virgin I met a girl that I am absolutly crazy abut and last night was our first time really trying to explore or sexuality togehter. So anyways she started playing with me and I would get a little hard but it went away qucikly however then we tried to have sex and I couldnt have an erection. I am so worried this is gonna hurt which otherwise is probably the best relationship ive ever had. I have jerked off alot in the past and usually can get a pretty good erection tho it isnt probably all what it should be unless I can get really turned which sometimes I will and get probably what is my maximum erection tho that is knida of strange. The other 2 girls ive been with both gave me blowjob and but neither time did I get a realy good erection. I mean this is like since back when I was 16 when I first got a blowjob and I still couldnt get an erection then. I should mention I am quiet overweight but I can do have pretty good endurance so it not really the problem.

This girl has already started questioning our relationship she says its not because of this but I really think it is. Please help me I dont want to throw away what might be the love of my life.